1 f\input texinfo @c -*-texinfo-*-
4 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
6 @c GNAT DOCUMENTATION o
10 @c GNAT is maintained by Ada Core Technologies Inc (http://www.gnat.com). o
12 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
14 @setfilename gnat_ugn.info
17 Copyright @copyright{} 1995-2009 Free Software Foundation,
20 Permission is granted to copy, distribute and/or modify this document
21 under the terms of the GNU Free Documentation License, Version 1.2 or
22 any later version published by the Free Software Foundation; with no
23 Invariant Sections, with no Front-Cover Texts and with no Back-Cover
24 Texts. A copy of the license is included in the section entitled
25 ``GNU Free Documentation License''.
28 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
30 @c GNAT_UGN Style Guide
32 @c 1. Always put a @noindent on the line before the first paragraph
33 @c after any of these commands:
45 @c 2. DO NOT use @example. Use @smallexample instead.
46 @c a) DO NOT use highlighting commands (@b{}, @i{}) inside an @smallexample
47 @c context. These can interfere with the readability of the texi
48 @c source file. Instead, use one of the following annotated
49 @c @smallexample commands, and preprocess the texi file with the
50 @c ada2texi tool (which generates appropriate highlighting):
51 @c @smallexample @c ada
52 @c @smallexample @c adanocomment
53 @c @smallexample @c projectfile
54 @c b) The "@c ada" markup will result in boldface for reserved words
55 @c and italics for comments
56 @c c) The "@c adanocomment" markup will result only in boldface for
57 @c reserved words (comments are left alone)
58 @c d) The "@c projectfile" markup is like "@c ada" except that the set
59 @c of reserved words include the new reserved words for project files
61 @c 3. Each @chapter, @section, @subsection, @subsubsection, etc.
62 @c command must be preceded by two empty lines
64 @c 4. The @item command should be on a line of its own if it is in an
65 @c @itemize or @enumerate command.
67 @c 5. When talking about ALI files use "ALI" (all uppercase), not "Ali"
70 @c 6. DO NOT put trailing spaces at the end of a line. Such spaces will
71 @c cause the document build to fail.
73 @c 7. DO NOT use @cartouche for examples that are longer than around 10 lines.
74 @c This command inhibits page breaks, so long examples in a @cartouche can
75 @c lead to large, ugly patches of empty space on a page.
77 @c NOTE: This file should be submitted to xgnatugn with either the vms flag
78 @c or the unw flag set. The unw flag covers topics for both Unix and
81 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
84 @c This flag is used where the text refers to conditions that exist when the
85 @c text was entered into the document but which may change over time.
86 @c Update the setting for the flag, and (if necessary) the text surrounding,
87 @c the references to the flag, on future doc revisions:
88 @c search for @value{NOW}.
92 @set DEFAULTLANGUAGEVERSION Ada 2005
93 @set NONDEFAULTLANGUAGEVERSION Ada 95
100 @set PLATFORM OpenVMS
105 @c The ARG is an optional argument. To be used for macro arguments in
106 @c their documentation (@defmac).
108 @r{[}@var{\varname\}@r{]}@c
111 @settitle @value{EDITION} User's Guide @value{PLATFORM}
112 @dircategory GNU Ada tools
114 * @value{EDITION} User's Guide: (gnat_ugn). @value{PLATFORM}
117 @include gcc-common.texi
119 @setchapternewpage odd
124 @title @value{EDITION} User's Guide
128 @titlefont{@i{@value{PLATFORM}}}
134 @subtitle GNAT, The GNU Ada Compiler
139 @vskip 0pt plus 1filll
146 @node Top, About This Guide, (dir), (dir)
147 @top @value{EDITION} User's Guide
150 @value{EDITION} User's Guide @value{PLATFORM}
153 GNAT, The GNU Ada Compiler@*
154 GCC version @value{version-GCC}@*
161 * Getting Started with GNAT::
162 * The GNAT Compilation Model::
163 * Compiling Using gcc::
164 * Binding Using gnatbind::
165 * Linking Using gnatlink::
166 * The GNAT Make Program gnatmake::
167 * Improving Performance::
168 * Renaming Files Using gnatchop::
169 * Configuration Pragmas::
170 * Handling Arbitrary File Naming Conventions Using gnatname::
171 * GNAT Project Manager::
172 * The Cross-Referencing Tools gnatxref and gnatfind::
173 * The GNAT Pretty-Printer gnatpp::
174 * The GNAT Metric Tool gnatmetric::
175 * File Name Krunching Using gnatkr::
176 * Preprocessing Using gnatprep::
178 * The GNAT Run-Time Library Builder gnatlbr::
180 * The GNAT Library Browser gnatls::
181 * Cleaning Up Using gnatclean::
183 * GNAT and Libraries::
184 * Using the GNU make Utility::
186 * Memory Management Issues::
187 * Stack Related Facilities::
188 * Verifying Properties Using gnatcheck::
189 * Creating Sample Bodies Using gnatstub::
190 * Generating Ada Bindings for C and C++ headers::
191 * Other Utility Programs::
192 * Running and Debugging Ada Programs::
194 * Code Coverage and Profiling::
197 * Compatibility with HP Ada::
199 * Platform-Specific Information for the Run-Time Libraries::
200 * Example of Binder Output File::
201 * Elaboration Order Handling in GNAT::
202 * Conditional Compilation::
204 * Compatibility and Porting Guide::
206 * Microsoft Windows Topics::
208 * GNU Free Documentation License::
211 --- The Detailed Node Listing ---
215 * What This Guide Contains::
216 * What You Should Know before Reading This Guide::
217 * Related Information::
220 Getting Started with GNAT
223 * Running a Simple Ada Program::
224 * Running a Program with Multiple Units::
225 * Using the gnatmake Utility::
227 * Editing with Emacs::
230 * Introduction to GPS::
233 The GNAT Compilation Model
235 * Source Representation::
236 * Foreign Language Representation::
237 * File Naming Rules::
238 * Using Other File Names::
239 * Alternative File Naming Schemes::
240 * Generating Object Files::
241 * Source Dependencies::
242 * The Ada Library Information Files::
243 * Binding an Ada Program::
244 * Mixed Language Programming::
246 * Building Mixed Ada & C++ Programs::
247 * Comparison between GNAT and C/C++ Compilation Models::
249 * Comparison between GNAT and Conventional Ada Library Models::
251 * Placement of temporary files::
254 Foreign Language Representation
257 * Other 8-Bit Codes::
258 * Wide Character Encodings::
260 Compiling Ada Programs With gcc
262 * Compiling Programs::
264 * Search Paths and the Run-Time Library (RTL)::
265 * Order of Compilation Issues::
270 * Output and Error Message Control::
271 * Warning Message Control::
272 * Debugging and Assertion Control::
273 * Validity Checking::
276 * Using gcc for Syntax Checking::
277 * Using gcc for Semantic Checking::
278 * Compiling Different Versions of Ada::
279 * Character Set Control::
280 * File Naming Control::
281 * Subprogram Inlining Control::
282 * Auxiliary Output Control::
283 * Debugging Control::
284 * Exception Handling Control::
285 * Units to Sources Mapping Files::
286 * Integrated Preprocessing::
291 Binding Ada Programs With gnatbind
294 * Switches for gnatbind::
295 * Command-Line Access::
296 * Search Paths for gnatbind::
297 * Examples of gnatbind Usage::
299 Switches for gnatbind
301 * Consistency-Checking Modes::
302 * Binder Error Message Control::
303 * Elaboration Control::
305 * Binding with Non-Ada Main Programs::
306 * Binding Programs with No Main Subprogram::
308 Linking Using gnatlink
311 * Switches for gnatlink::
313 The GNAT Make Program gnatmake
316 * Switches for gnatmake::
317 * Mode Switches for gnatmake::
318 * Notes on the Command Line::
319 * How gnatmake Works::
320 * Examples of gnatmake Usage::
322 Improving Performance
323 * Performance Considerations::
324 * Text_IO Suggestions::
325 * Reducing Size of Ada Executables with gnatelim::
326 * Reducing Size of Executables with unused subprogram/data elimination::
328 Performance Considerations
329 * Controlling Run-Time Checks::
330 * Use of Restrictions::
331 * Optimization Levels::
332 * Debugging Optimized Code::
333 * Inlining of Subprograms::
334 * Other Optimization Switches::
335 * Optimization and Strict Aliasing::
337 * Coverage Analysis::
340 Reducing Size of Ada Executables with gnatelim
343 * Correcting the List of Eliminate Pragmas::
344 * Making Your Executables Smaller::
345 * Summary of the gnatelim Usage Cycle::
347 Reducing Size of Executables with unused subprogram/data elimination
348 * About unused subprogram/data elimination::
349 * Compilation options::
351 Renaming Files Using gnatchop
353 * Handling Files with Multiple Units::
354 * Operating gnatchop in Compilation Mode::
355 * Command Line for gnatchop::
356 * Switches for gnatchop::
357 * Examples of gnatchop Usage::
359 Configuration Pragmas
361 * Handling of Configuration Pragmas::
362 * The Configuration Pragmas Files::
364 Handling Arbitrary File Naming Conventions Using gnatname
366 * Arbitrary File Naming Conventions::
368 * Switches for gnatname::
369 * Examples of gnatname Usage::
374 * Examples of Project Files::
375 * Project File Syntax::
376 * Objects and Sources in Project Files::
377 * Importing Projects::
378 * Project Extension::
379 * Project Hierarchy Extension::
380 * External References in Project Files::
381 * Packages in Project Files::
382 * Variables from Imported Projects::
385 * Stand-alone Library Projects::
386 * Switches Related to Project Files::
387 * Tools Supporting Project Files::
388 * An Extended Example::
389 * Project File Complete Syntax::
391 The Cross-Referencing Tools gnatxref and gnatfind
393 * gnatxref Switches::
394 * gnatfind Switches::
395 * Project Files for gnatxref and gnatfind::
396 * Regular Expressions in gnatfind and gnatxref::
397 * Examples of gnatxref Usage::
398 * Examples of gnatfind Usage::
400 The GNAT Pretty-Printer gnatpp
402 * Switches for gnatpp::
405 The GNAT Metrics Tool gnatmetric
407 * Switches for gnatmetric::
409 File Name Krunching Using gnatkr
414 * Examples of gnatkr Usage::
416 Preprocessing Using gnatprep
417 * Preprocessing Symbols::
419 * Switches for gnatprep::
420 * Form of Definitions File::
421 * Form of Input Text for gnatprep::
424 The GNAT Run-Time Library Builder gnatlbr
427 * Switches for gnatlbr::
428 * Examples of gnatlbr Usage::
431 The GNAT Library Browser gnatls
434 * Switches for gnatls::
435 * Examples of gnatls Usage::
437 Cleaning Up Using gnatclean
439 * Running gnatclean::
440 * Switches for gnatclean::
441 @c * Examples of gnatclean Usage::
447 * Introduction to Libraries in GNAT::
448 * General Ada Libraries::
449 * Stand-alone Ada Libraries::
450 * Rebuilding the GNAT Run-Time Library::
452 Using the GNU make Utility
454 * Using gnatmake in a Makefile::
455 * Automatically Creating a List of Directories::
456 * Generating the Command Line Switches::
457 * Overcoming Command Line Length Limits::
460 Memory Management Issues
462 * Some Useful Memory Pools::
463 * The GNAT Debug Pool Facility::
468 Stack Related Facilities
470 * Stack Overflow Checking::
471 * Static Stack Usage Analysis::
472 * Dynamic Stack Usage Analysis::
474 Some Useful Memory Pools
476 The GNAT Debug Pool Facility
482 * Switches for gnatmem::
483 * Example of gnatmem Usage::
486 Verifying Properties Using gnatcheck
488 * Format of the Report File::
489 * General gnatcheck Switches::
490 * gnatcheck Rule Options::
491 * Adding the Results of Compiler Checks to gnatcheck Output::
492 * Project-Wide Checks::
495 Sample Bodies Using gnatstub
498 * Switches for gnatstub::
500 Other Utility Programs
502 * Using Other Utility Programs with GNAT::
503 * The External Symbol Naming Scheme of GNAT::
504 * Converting Ada Files to html with gnathtml::
507 Code Coverage and Profiling
509 * Code Coverage of Ada Programs using gcov::
510 * Profiling an Ada Program using gprof::
513 Running and Debugging Ada Programs
515 * The GNAT Debugger GDB::
517 * Introduction to GDB Commands::
518 * Using Ada Expressions::
519 * Calling User-Defined Subprograms::
520 * Using the Next Command in a Function::
523 * Debugging Generic Units::
524 * GNAT Abnormal Termination or Failure to Terminate::
525 * Naming Conventions for GNAT Source Files::
526 * Getting Internal Debugging Information::
534 Compatibility with HP Ada
536 * Ada Language Compatibility::
537 * Differences in the Definition of Package System::
538 * Language-Related Features::
539 * The Package STANDARD::
540 * The Package SYSTEM::
541 * Tasking and Task-Related Features::
542 * Pragmas and Pragma-Related Features::
543 * Library of Predefined Units::
545 * Main Program Definition::
546 * Implementation-Defined Attributes::
547 * Compiler and Run-Time Interfacing::
548 * Program Compilation and Library Management::
550 * Implementation Limits::
551 * Tools and Utilities::
553 Language-Related Features
555 * Integer Types and Representations::
556 * Floating-Point Types and Representations::
557 * Pragmas Float_Representation and Long_Float::
558 * Fixed-Point Types and Representations::
559 * Record and Array Component Alignment::
561 * Other Representation Clauses::
563 Tasking and Task-Related Features
565 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
566 * Assigning Task IDs::
567 * Task IDs and Delays::
568 * Task-Related Pragmas::
569 * Scheduling and Task Priority::
571 * External Interrupts::
573 Pragmas and Pragma-Related Features
575 * Restrictions on the Pragma INLINE::
576 * Restrictions on the Pragma INTERFACE::
577 * Restrictions on the Pragma SYSTEM_NAME::
579 Library of Predefined Units
581 * Changes to DECLIB::
585 * Shared Libraries and Options Files::
589 Platform-Specific Information for the Run-Time Libraries
591 * Summary of Run-Time Configurations::
592 * Specifying a Run-Time Library::
593 * Choosing the Scheduling Policy::
594 * Solaris-Specific Considerations::
595 * Linux-Specific Considerations::
596 * AIX-Specific Considerations::
597 * Irix-Specific Considerations::
599 Example of Binder Output File
601 Elaboration Order Handling in GNAT
604 * Checking the Elaboration Order::
605 * Controlling the Elaboration Order::
606 * Controlling Elaboration in GNAT - Internal Calls::
607 * Controlling Elaboration in GNAT - External Calls::
608 * Default Behavior in GNAT - Ensuring Safety::
609 * Treatment of Pragma Elaborate::
610 * Elaboration Issues for Library Tasks::
611 * Mixing Elaboration Models::
612 * What to Do If the Default Elaboration Behavior Fails::
613 * Elaboration for Access-to-Subprogram Values::
614 * Summary of Procedures for Elaboration Control::
615 * Other Elaboration Order Considerations::
617 Conditional Compilation
618 * Use of Boolean Constants::
619 * Debugging - A Special Case::
620 * Conditionalizing Declarations::
621 * Use of Alternative Implementations::
626 * Basic Assembler Syntax::
627 * A Simple Example of Inline Assembler::
628 * Output Variables in Inline Assembler::
629 * Input Variables in Inline Assembler::
630 * Inlining Inline Assembler Code::
631 * Other Asm Functionality::
633 Compatibility and Porting Guide
635 * Compatibility with Ada 83::
636 * Compatibility between Ada 95 and Ada 2005::
637 * Implementation-dependent characteristics::
639 @c This brief section is only in the non-VMS version
640 @c The complete chapter on HP Ada issues is in the VMS version
641 * Compatibility with HP Ada 83::
643 * Compatibility with Other Ada Systems::
644 * Representation Clauses::
646 * Transitioning to 64-Bit GNAT for OpenVMS::
650 Microsoft Windows Topics
652 * Using GNAT on Windows::
653 * CONSOLE and WINDOWS subsystems::
655 * Mixed-Language Programming on Windows::
656 * Windows Calling Conventions::
657 * Introduction to Dynamic Link Libraries (DLLs)::
658 * Using DLLs with GNAT::
659 * Building DLLs with GNAT::
660 * GNAT and Windows Resources::
662 * Setting Stack Size from gnatlink::
663 * Setting Heap Size from gnatlink::
670 @node About This Guide
671 @unnumbered About This Guide
675 This guide describes the use of @value{EDITION},
676 a compiler and software development toolset for the full Ada
677 programming language, implemented on OpenVMS for HP's Alpha and
678 Integrity server (I64) platforms.
681 This guide describes the use of @value{EDITION},
682 a compiler and software development
683 toolset for the full Ada programming language.
685 It documents the features of the compiler and tools, and explains
686 how to use them to build Ada applications.
688 @value{EDITION} implements Ada 95 and Ada 2005, and it may also be invoked in
689 Ada 83 compatibility mode.
690 By default, @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
691 but you can override with a compiler switch
692 (@pxref{Compiling Different Versions of Ada})
693 to explicitly specify the language version.
694 Throughout this manual, references to ``Ada'' without a year suffix
695 apply to both the Ada 95 and Ada 2005 versions of the language.
699 For ease of exposition, ``@value{EDITION}'' will be referred to simply as
700 ``GNAT'' in the remainder of this document.
707 * What This Guide Contains::
708 * What You Should Know before Reading This Guide::
709 * Related Information::
713 @node What This Guide Contains
714 @unnumberedsec What This Guide Contains
717 This guide contains the following chapters:
721 @ref{Getting Started with GNAT}, describes how to get started compiling
722 and running Ada programs with the GNAT Ada programming environment.
724 @ref{The GNAT Compilation Model}, describes the compilation model used
728 @ref{Compiling Using gcc}, describes how to compile
729 Ada programs with @command{gcc}, the Ada compiler.
732 @ref{Binding Using gnatbind}, describes how to
733 perform binding of Ada programs with @code{gnatbind}, the GNAT binding
737 @ref{Linking Using gnatlink},
738 describes @command{gnatlink}, a
739 program that provides for linking using the GNAT run-time library to
740 construct a program. @command{gnatlink} can also incorporate foreign language
741 object units into the executable.
744 @ref{The GNAT Make Program gnatmake}, describes @command{gnatmake}, a
745 utility that automatically determines the set of sources
746 needed by an Ada compilation unit, and executes the necessary compilations
750 @ref{Improving Performance}, shows various techniques for making your
751 Ada program run faster or take less space.
752 It discusses the effect of the compiler's optimization switch and
753 also describes the @command{gnatelim} tool and unused subprogram/data
757 @ref{Renaming Files Using gnatchop}, describes
758 @code{gnatchop}, a utility that allows you to preprocess a file that
759 contains Ada source code, and split it into one or more new files, one
760 for each compilation unit.
763 @ref{Configuration Pragmas}, describes the configuration pragmas
767 @ref{Handling Arbitrary File Naming Conventions Using gnatname},
768 shows how to override the default GNAT file naming conventions,
769 either for an individual unit or globally.
772 @ref{GNAT Project Manager}, describes how to use project files
773 to organize large projects.
776 @ref{The Cross-Referencing Tools gnatxref and gnatfind}, discusses
777 @code{gnatxref} and @code{gnatfind}, two tools that provide an easy
778 way to navigate through sources.
781 @ref{The GNAT Pretty-Printer gnatpp}, shows how to produce a reformatted
782 version of an Ada source file with control over casing, indentation,
783 comment placement, and other elements of program presentation style.
786 @ref{The GNAT Metric Tool gnatmetric}, shows how to compute various
787 metrics for an Ada source file, such as the number of types and subprograms,
788 and assorted complexity measures.
791 @ref{File Name Krunching Using gnatkr}, describes the @code{gnatkr}
792 file name krunching utility, used to handle shortened
793 file names on operating systems with a limit on the length of names.
796 @ref{Preprocessing Using gnatprep}, describes @code{gnatprep}, a
797 preprocessor utility that allows a single source file to be used to
798 generate multiple or parameterized source files by means of macro
803 @ref{The GNAT Run-Time Library Builder gnatlbr}, describes @command{gnatlbr},
804 a tool for rebuilding the GNAT run time with user-supplied
805 configuration pragmas.
809 @ref{The GNAT Library Browser gnatls}, describes @code{gnatls}, a
810 utility that displays information about compiled units, including dependences
811 on the corresponding sources files, and consistency of compilations.
814 @ref{Cleaning Up Using gnatclean}, describes @code{gnatclean}, a utility
815 to delete files that are produced by the compiler, binder and linker.
819 @ref{GNAT and Libraries}, describes the process of creating and using
820 Libraries with GNAT. It also describes how to recompile the GNAT run-time
824 @ref{Using the GNU make Utility}, describes some techniques for using
825 the GNAT toolset in Makefiles.
829 @ref{Memory Management Issues}, describes some useful predefined storage pools
830 and in particular the GNAT Debug Pool facility, which helps detect incorrect
833 It also describes @command{gnatmem}, a utility that monitors dynamic
834 allocation and deallocation and helps detect ``memory leaks''.
838 @ref{Stack Related Facilities}, describes some useful tools associated with
839 stack checking and analysis.
842 @ref{Verifying Properties Using gnatcheck}, discusses @code{gnatcheck},
843 a utility that checks Ada code against a set of rules.
846 @ref{Creating Sample Bodies Using gnatstub}, discusses @code{gnatstub},
847 a utility that generates empty but compilable bodies for library units.
850 @ref{Generating Ada Bindings for C and C++ headers}, describes how to
851 generate automatically Ada bindings from C and C++ headers.
854 @ref{Other Utility Programs}, discusses several other GNAT utilities,
855 including @code{gnathtml}.
859 @ref{Code Coverage and Profiling}, describes how to perform a structural
860 coverage and profile the execution of Ada programs.
864 @ref{Running and Debugging Ada Programs}, describes how to run and debug
869 @ref{Compatibility with HP Ada}, details the compatibility of GNAT with
870 HP Ada 83 @footnote{``HP Ada'' refers to the legacy product originally
871 developed by Digital Equipment Corporation and currently supported by HP.}
872 for OpenVMS Alpha. This product was formerly known as DEC Ada,
875 historical compatibility reasons, the relevant libraries still use the
880 @ref{Platform-Specific Information for the Run-Time Libraries},
881 describes the various run-time
882 libraries supported by GNAT on various platforms and explains how to
883 choose a particular library.
886 @ref{Example of Binder Output File}, shows the source code for the binder
887 output file for a sample program.
890 @ref{Elaboration Order Handling in GNAT}, describes how GNAT helps
891 you deal with elaboration order issues.
894 @ref{Conditional Compilation}, describes how to model conditional compilation,
895 both with Ada in general and with GNAT facilities in particular.
898 @ref{Inline Assembler}, shows how to use the inline assembly facility
902 @ref{Compatibility and Porting Guide}, contains sections on compatibility
903 of GNAT with other Ada development environments (including Ada 83 systems),
904 to assist in porting code from those environments.
908 @ref{Microsoft Windows Topics}, presents information relevant to the
909 Microsoft Windows platform.
913 @c *************************************************
914 @node What You Should Know before Reading This Guide
915 @c *************************************************
916 @unnumberedsec What You Should Know before Reading This Guide
918 @cindex Ada 95 Language Reference Manual
919 @cindex Ada 2005 Language Reference Manual
921 This guide assumes a basic familiarity with the Ada 95 language, as
922 described in the International Standard ANSI/ISO/IEC-8652:1995, January
924 It does not require knowledge of the new features introduced by Ada 2005,
925 (officially known as ISO/IEC 8652:1995 with Technical Corrigendum 1
927 Both reference manuals are included in the GNAT documentation
930 @node Related Information
931 @unnumberedsec Related Information
934 For further information about related tools, refer to the following
939 @xref{Top, GNAT Reference Manual, About This Guide, gnat_rm, GNAT
940 Reference Manual}, which contains all reference material for the GNAT
941 implementation of Ada.
945 @cite{Using the GNAT Programming Studio}, which describes the GPS
946 Integrated Development Environment.
949 @cite{GNAT Programming Studio Tutorial}, which introduces the
950 main GPS features through examples.
954 @cite{Ada 95 Reference Manual}, which contains reference
955 material for the Ada 95 programming language.
958 @cite{Ada 2005 Reference Manual}, which contains reference
959 material for the Ada 2005 programming language.
962 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
964 in the GNU:[DOCS] directory,
966 for all details on the use of the GNU source-level debugger.
969 @xref{Top,, The extensible self-documenting text editor, emacs,
972 located in the GNU:[DOCS] directory if the EMACS kit is installed,
974 for full information on the extensible editor and programming
981 @unnumberedsec Conventions
983 @cindex Typographical conventions
986 Following are examples of the typographical and graphic conventions used
991 @code{Functions}, @command{utility program names}, @code{standard names},
995 @option{Option flags}
998 @file{File names}, @samp{button names}, and @samp{field names}.
1001 @code{Variables}, @env{environment variables}, and @var{metasyntactic
1008 @r{[}optional information or parameters@r{]}
1011 Examples are described by text
1013 and then shown this way.
1018 Commands that are entered by the user are preceded in this manual by the
1019 characters @w{``@code{$ }''} (dollar sign followed by space). If your system
1020 uses this sequence as a prompt, then the commands will appear exactly as
1021 you see them in the manual. If your system uses some other prompt, then
1022 the command will appear with the @code{$} replaced by whatever prompt
1023 character you are using.
1026 Full file names are shown with the ``@code{/}'' character
1027 as the directory separator; e.g., @file{parent-dir/subdir/myfile.adb}.
1028 If you are using GNAT on a Windows platform, please note that
1029 the ``@code{\}'' character should be used instead.
1032 @c ****************************
1033 @node Getting Started with GNAT
1034 @chapter Getting Started with GNAT
1037 This chapter describes some simple ways of using GNAT to build
1038 executable Ada programs.
1040 @ref{Running GNAT}, through @ref{Using the gnatmake Utility},
1041 show how to use the command line environment.
1042 @ref{Introduction to GPS}, provides a brief
1043 introduction to the GNAT Programming Studio, a visually-oriented
1044 Integrated Development Environment for GNAT.
1045 GPS offers a graphical ``look and feel'', support for development in
1046 other programming languages, comprehensive browsing features, and
1047 many other capabilities.
1048 For information on GPS please refer to
1049 @cite{Using the GNAT Programming Studio}.
1054 * Running a Simple Ada Program::
1055 * Running a Program with Multiple Units::
1056 * Using the gnatmake Utility::
1058 * Editing with Emacs::
1061 * Introduction to GPS::
1066 @section Running GNAT
1069 Three steps are needed to create an executable file from an Ada source
1074 The source file(s) must be compiled.
1076 The file(s) must be bound using the GNAT binder.
1078 All appropriate object files must be linked to produce an executable.
1082 All three steps are most commonly handled by using the @command{gnatmake}
1083 utility program that, given the name of the main program, automatically
1084 performs the necessary compilation, binding and linking steps.
1086 @node Running a Simple Ada Program
1087 @section Running a Simple Ada Program
1090 Any text editor may be used to prepare an Ada program.
1092 used, the optional Ada mode may be helpful in laying out the program.)
1094 program text is a normal text file. We will assume in our initial
1095 example that you have used your editor to prepare the following
1096 standard format text file:
1098 @smallexample @c ada
1100 with Ada.Text_IO; use Ada.Text_IO;
1103 Put_Line ("Hello WORLD!");
1109 This file should be named @file{hello.adb}.
1110 With the normal default file naming conventions, GNAT requires
1112 contain a single compilation unit whose file name is the
1114 with periods replaced by hyphens; the
1115 extension is @file{ads} for a
1116 spec and @file{adb} for a body.
1117 You can override this default file naming convention by use of the
1118 special pragma @code{Source_File_Name} (@pxref{Using Other File Names}).
1119 Alternatively, if you want to rename your files according to this default
1120 convention, which is probably more convenient if you will be using GNAT
1121 for all your compilations, then the @code{gnatchop} utility
1122 can be used to generate correctly-named source files
1123 (@pxref{Renaming Files Using gnatchop}).
1125 You can compile the program using the following command (@code{$} is used
1126 as the command prompt in the examples in this document):
1133 @command{gcc} is the command used to run the compiler. This compiler is
1134 capable of compiling programs in several languages, including Ada and
1135 C. It assumes that you have given it an Ada program if the file extension is
1136 either @file{.ads} or @file{.adb}, and it will then call
1137 the GNAT compiler to compile the specified file.
1140 The @option{-c} switch is required. It tells @command{gcc} to only do a
1141 compilation. (For C programs, @command{gcc} can also do linking, but this
1142 capability is not used directly for Ada programs, so the @option{-c}
1143 switch must always be present.)
1146 This compile command generates a file
1147 @file{hello.o}, which is the object
1148 file corresponding to your Ada program. It also generates
1149 an ``Ada Library Information'' file @file{hello.ali},
1150 which contains additional information used to check
1151 that an Ada program is consistent.
1152 To build an executable file,
1153 use @code{gnatbind} to bind the program
1154 and @command{gnatlink} to link it. The
1155 argument to both @code{gnatbind} and @command{gnatlink} is the name of the
1156 @file{ALI} file, but the default extension of @file{.ali} can
1157 be omitted. This means that in the most common case, the argument
1158 is simply the name of the main program:
1166 A simpler method of carrying out these steps is to use
1168 a master program that invokes all the required
1169 compilation, binding and linking tools in the correct order. In particular,
1170 @command{gnatmake} automatically recompiles any sources that have been
1171 modified since they were last compiled, or sources that depend
1172 on such modified sources, so that ``version skew'' is avoided.
1173 @cindex Version skew (avoided by @command{gnatmake})
1176 $ gnatmake hello.adb
1180 The result is an executable program called @file{hello}, which can be
1188 assuming that the current directory is on the search path
1189 for executable programs.
1192 and, if all has gone well, you will see
1199 appear in response to this command.
1201 @c ****************************************
1202 @node Running a Program with Multiple Units
1203 @section Running a Program with Multiple Units
1206 Consider a slightly more complicated example that has three files: a
1207 main program, and the spec and body of a package:
1209 @smallexample @c ada
1212 package Greetings is
1217 with Ada.Text_IO; use Ada.Text_IO;
1218 package body Greetings is
1221 Put_Line ("Hello WORLD!");
1224 procedure Goodbye is
1226 Put_Line ("Goodbye WORLD!");
1243 Following the one-unit-per-file rule, place this program in the
1244 following three separate files:
1248 spec of package @code{Greetings}
1251 body of package @code{Greetings}
1254 body of main program
1258 To build an executable version of
1259 this program, we could use four separate steps to compile, bind, and link
1260 the program, as follows:
1264 $ gcc -c greetings.adb
1270 Note that there is no required order of compilation when using GNAT.
1271 In particular it is perfectly fine to compile the main program first.
1272 Also, it is not necessary to compile package specs in the case where
1273 there is an accompanying body; you only need to compile the body. If you want
1274 to submit these files to the compiler for semantic checking and not code
1275 generation, then use the
1276 @option{-gnatc} switch:
1279 $ gcc -c greetings.ads -gnatc
1283 Although the compilation can be done in separate steps as in the
1284 above example, in practice it is almost always more convenient
1285 to use the @command{gnatmake} tool. All you need to know in this case
1286 is the name of the main program's source file. The effect of the above four
1287 commands can be achieved with a single one:
1290 $ gnatmake gmain.adb
1294 In the next section we discuss the advantages of using @command{gnatmake} in
1297 @c *****************************
1298 @node Using the gnatmake Utility
1299 @section Using the @command{gnatmake} Utility
1302 If you work on a program by compiling single components at a time using
1303 @command{gcc}, you typically keep track of the units you modify. In order to
1304 build a consistent system, you compile not only these units, but also any
1305 units that depend on the units you have modified.
1306 For example, in the preceding case,
1307 if you edit @file{gmain.adb}, you only need to recompile that file. But if
1308 you edit @file{greetings.ads}, you must recompile both
1309 @file{greetings.adb} and @file{gmain.adb}, because both files contain
1310 units that depend on @file{greetings.ads}.
1312 @code{gnatbind} will warn you if you forget one of these compilation
1313 steps, so that it is impossible to generate an inconsistent program as a
1314 result of forgetting to do a compilation. Nevertheless it is tedious and
1315 error-prone to keep track of dependencies among units.
1316 One approach to handle the dependency-bookkeeping is to use a
1317 makefile. However, makefiles present maintenance problems of their own:
1318 if the dependencies change as you change the program, you must make
1319 sure that the makefile is kept up-to-date manually, which is also an
1320 error-prone process.
1322 The @command{gnatmake} utility takes care of these details automatically.
1323 Invoke it using either one of the following forms:
1326 $ gnatmake gmain.adb
1327 $ gnatmake ^gmain^GMAIN^
1331 The argument is the name of the file containing the main program;
1332 you may omit the extension. @command{gnatmake}
1333 examines the environment, automatically recompiles any files that need
1334 recompiling, and binds and links the resulting set of object files,
1335 generating the executable file, @file{^gmain^GMAIN.EXE^}.
1336 In a large program, it
1337 can be extremely helpful to use @command{gnatmake}, because working out by hand
1338 what needs to be recompiled can be difficult.
1340 Note that @command{gnatmake}
1341 takes into account all the Ada rules that
1342 establish dependencies among units. These include dependencies that result
1343 from inlining subprogram bodies, and from
1344 generic instantiation. Unlike some other
1345 Ada make tools, @command{gnatmake} does not rely on the dependencies that were
1346 found by the compiler on a previous compilation, which may possibly
1347 be wrong when sources change. @command{gnatmake} determines the exact set of
1348 dependencies from scratch each time it is run.
1351 @node Editing with Emacs
1352 @section Editing with Emacs
1356 Emacs is an extensible self-documenting text editor that is available in a
1357 separate VMSINSTAL kit.
1359 Invoke Emacs by typing @kbd{Emacs} at the command prompt. To get started,
1360 click on the Emacs Help menu and run the Emacs Tutorial.
1361 In a character cell terminal, Emacs help is invoked with @kbd{Ctrl-h} (also
1362 written as @kbd{C-h}), and the tutorial by @kbd{C-h t}.
1364 Documentation on Emacs and other tools is available in Emacs under the
1365 pull-down menu button: @code{Help - Info}. After selecting @code{Info},
1366 use the middle mouse button to select a topic (e.g.@: Emacs).
1368 In a character cell terminal, do @kbd{C-h i} to invoke info, and then @kbd{m}
1369 (stands for menu) followed by the menu item desired, as in @kbd{m Emacs}, to
1370 get to the Emacs manual.
1371 Help on Emacs is also available by typing @kbd{HELP EMACS} at the DCL command
1374 The tutorial is highly recommended in order to learn the intricacies of Emacs,
1375 which is sufficiently extensible to provide for a complete programming
1376 environment and shell for the sophisticated user.
1380 @node Introduction to GPS
1381 @section Introduction to GPS
1382 @cindex GPS (GNAT Programming Studio)
1383 @cindex GNAT Programming Studio (GPS)
1385 Although the command line interface (@command{gnatmake}, etc.) alone
1386 is sufficient, a graphical Interactive Development
1387 Environment can make it easier for you to compose, navigate, and debug
1388 programs. This section describes the main features of GPS
1389 (``GNAT Programming Studio''), the GNAT graphical IDE.
1390 You will see how to use GPS to build and debug an executable, and
1391 you will also learn some of the basics of the GNAT ``project'' facility.
1393 GPS enables you to do much more than is presented here;
1394 e.g., you can produce a call graph, interface to a third-party
1395 Version Control System, and inspect the generated assembly language
1397 Indeed, GPS also supports languages other than Ada.
1398 Such additional information, and an explanation of all of the GPS menu
1399 items. may be found in the on-line help, which includes
1400 a user's guide and a tutorial (these are also accessible from the GNAT
1404 * Building a New Program with GPS::
1405 * Simple Debugging with GPS::
1408 @node Building a New Program with GPS
1409 @subsection Building a New Program with GPS
1411 GPS invokes the GNAT compilation tools using information
1412 contained in a @emph{project} (also known as a @emph{project file}):
1413 a collection of properties such
1414 as source directories, identities of main subprograms, tool switches, etc.,
1415 and their associated values.
1416 See @ref{GNAT Project Manager} for details.
1417 In order to run GPS, you will need to either create a new project
1418 or else open an existing one.
1420 This section will explain how you can use GPS to create a project,
1421 to associate Ada source files with a project, and to build and run
1425 @item @emph{Creating a project}
1427 Invoke GPS, either from the command line or the platform's IDE.
1428 After it starts, GPS will display a ``Welcome'' screen with three
1433 @code{Start with default project in directory}
1436 @code{Create new project with wizard}
1439 @code{Open existing project}
1443 Select @code{Create new project with wizard} and press @code{OK}.
1444 A new window will appear. In the text box labeled with
1445 @code{Enter the name of the project to create}, type @file{sample}
1446 as the project name.
1447 In the next box, browse to choose the directory in which you
1448 would like to create the project file.
1449 After selecting an appropriate directory, press @code{Forward}.
1451 A window will appear with the title
1452 @code{Version Control System Configuration}.
1453 Simply press @code{Forward}.
1455 A window will appear with the title
1456 @code{Please select the source directories for this project}.
1457 The directory that you specified for the project file will be selected
1458 by default as the one to use for sources; simply press @code{Forward}.
1460 A window will appear with the title
1461 @code{Please select the build directory for this project}.
1462 The directory that you specified for the project file will be selected
1463 by default for object files and executables;
1464 simply press @code{Forward}.
1466 A window will appear with the title
1467 @code{Please select the main units for this project}.
1468 You will supply this information later, after creating the source file.
1469 Simply press @code{Forward} for now.
1471 A window will appear with the title
1472 @code{Please select the switches to build the project}.
1473 Press @code{Apply}. This will create a project file named
1474 @file{sample.prj} in the directory that you had specified.
1476 @item @emph{Creating and saving the source file}
1478 After you create the new project, a GPS window will appear, which is
1479 partitioned into two main sections:
1483 A @emph{Workspace area}, initially greyed out, which you will use for
1484 creating and editing source files
1487 Directly below, a @emph{Messages area}, which initially displays a
1488 ``Welcome'' message.
1489 (If the Messages area is not visible, drag its border upward to expand it.)
1493 Select @code{File} on the menu bar, and then the @code{New} command.
1494 The Workspace area will become white, and you can now
1495 enter the source program explicitly.
1496 Type the following text
1498 @smallexample @c ada
1500 with Ada.Text_IO; use Ada.Text_IO;
1503 Put_Line("Hello from GPS!");
1509 Select @code{File}, then @code{Save As}, and enter the source file name
1511 The file will be saved in the same directory you specified as the
1512 location of the default project file.
1514 @item @emph{Updating the project file}
1516 You need to add the new source file to the project.
1518 the @code{Project} menu and then @code{Edit project properties}.
1519 Click the @code{Main files} tab on the left, and then the
1521 Choose @file{hello.adb} from the list, and press @code{Open}.
1522 The project settings window will reflect this action.
1525 @item @emph{Building and running the program}
1527 In the main GPS window, now choose the @code{Build} menu, then @code{Make},
1528 and select @file{hello.adb}.
1529 The Messages window will display the resulting invocations of @command{gcc},
1530 @command{gnatbind}, and @command{gnatlink}
1531 (reflecting the default switch settings from the
1532 project file that you created) and then a ``successful compilation/build''
1535 To run the program, choose the @code{Build} menu, then @code{Run}, and
1536 select @command{hello}.
1537 An @emph{Arguments Selection} window will appear.
1538 There are no command line arguments, so just click @code{OK}.
1540 The Messages window will now display the program's output (the string
1541 @code{Hello from GPS}), and at the bottom of the GPS window a status
1542 update is displayed (@code{Run: hello}).
1543 Close the GPS window (or select @code{File}, then @code{Exit}) to
1544 terminate this GPS session.
1547 @node Simple Debugging with GPS
1548 @subsection Simple Debugging with GPS
1550 This section illustrates basic debugging techniques (setting breakpoints,
1551 examining/modifying variables, single stepping).
1554 @item @emph{Opening a project}
1556 Start GPS and select @code{Open existing project}; browse to
1557 specify the project file @file{sample.prj} that you had created in the
1560 @item @emph{Creating a source file}
1562 Select @code{File}, then @code{New}, and type in the following program:
1564 @smallexample @c ada
1566 with Ada.Text_IO; use Ada.Text_IO;
1567 procedure Example is
1568 Line : String (1..80);
1571 Put_Line("Type a line of text at each prompt; an empty line to exit");
1575 Put_Line (Line (1..N) );
1583 Select @code{File}, then @code{Save as}, and enter the file name
1586 @item @emph{Updating the project file}
1588 Add @code{Example} as a new main unit for the project:
1591 Select @code{Project}, then @code{Edit Project Properties}.
1594 Select the @code{Main files} tab, click @code{Add}, then
1595 select the file @file{example.adb} from the list, and
1597 You will see the file name appear in the list of main units
1603 @item @emph{Building/running the executable}
1605 To build the executable
1606 select @code{Build}, then @code{Make}, and then choose @file{example.adb}.
1608 Run the program to see its effect (in the Messages area).
1609 Each line that you enter is displayed; an empty line will
1610 cause the loop to exit and the program to terminate.
1612 @item @emph{Debugging the program}
1614 Note that the @option{-g} switches to @command{gcc} and @command{gnatlink},
1615 which are required for debugging, are on by default when you create
1617 Thus unless you intentionally remove these settings, you will be able
1618 to debug any program that you develop using GPS.
1621 @item @emph{Initializing}
1623 Select @code{Debug}, then @code{Initialize}, then @file{example}
1625 @item @emph{Setting a breakpoint}
1627 After performing the initialization step, you will observe a small
1628 icon to the right of each line number.
1629 This serves as a toggle for breakpoints; clicking the icon will
1630 set a breakpoint at the corresponding line (the icon will change to
1631 a red circle with an ``x''), and clicking it again
1632 will remove the breakpoint / reset the icon.
1634 For purposes of this example, set a breakpoint at line 10 (the
1635 statement @code{Put_Line@ (Line@ (1..N));}
1637 @item @emph{Starting program execution}
1639 Select @code{Debug}, then @code{Run}. When the
1640 @code{Program Arguments} window appears, click @code{OK}.
1641 A console window will appear; enter some line of text,
1642 e.g.@: @code{abcde}, at the prompt.
1643 The program will pause execution when it gets to the
1644 breakpoint, and the corresponding line is highlighted.
1646 @item @emph{Examining a variable}
1648 Move the mouse over one of the occurrences of the variable @code{N}.
1649 You will see the value (5) displayed, in ``tool tip'' fashion.
1650 Right click on @code{N}, select @code{Debug}, then select @code{Display N}.
1651 You will see information about @code{N} appear in the @code{Debugger Data}
1652 pane, showing the value as 5.
1654 @item @emph{Assigning a new value to a variable}
1656 Right click on the @code{N} in the @code{Debugger Data} pane, and
1657 select @code{Set value of N}.
1658 When the input window appears, enter the value @code{4} and click
1660 This value does not automatically appear in the @code{Debugger Data}
1661 pane; to see it, right click again on the @code{N} in the
1662 @code{Debugger Data} pane and select @code{Update value}.
1663 The new value, 4, will appear in red.
1665 @item @emph{Single stepping}
1667 Select @code{Debug}, then @code{Next}.
1668 This will cause the next statement to be executed, in this case the
1669 call of @code{Put_Line} with the string slice.
1670 Notice in the console window that the displayed string is simply
1671 @code{abcd} and not @code{abcde} which you had entered.
1672 This is because the upper bound of the slice is now 4 rather than 5.
1674 @item @emph{Removing a breakpoint}
1676 Toggle the breakpoint icon at line 10.
1678 @item @emph{Resuming execution from a breakpoint}
1680 Select @code{Debug}, then @code{Continue}.
1681 The program will reach the next iteration of the loop, and
1682 wait for input after displaying the prompt.
1683 This time, just hit the @kbd{Enter} key.
1684 The value of @code{N} will be 0, and the program will terminate.
1685 The console window will disappear.
1690 @node The GNAT Compilation Model
1691 @chapter The GNAT Compilation Model
1692 @cindex GNAT compilation model
1693 @cindex Compilation model
1696 * Source Representation::
1697 * Foreign Language Representation::
1698 * File Naming Rules::
1699 * Using Other File Names::
1700 * Alternative File Naming Schemes::
1701 * Generating Object Files::
1702 * Source Dependencies::
1703 * The Ada Library Information Files::
1704 * Binding an Ada Program::
1705 * Mixed Language Programming::
1707 * Building Mixed Ada & C++ Programs::
1708 * Comparison between GNAT and C/C++ Compilation Models::
1710 * Comparison between GNAT and Conventional Ada Library Models::
1712 * Placement of temporary files::
1717 This chapter describes the compilation model used by GNAT. Although
1718 similar to that used by other languages, such as C and C++, this model
1719 is substantially different from the traditional Ada compilation models,
1720 which are based on a library. The model is initially described without
1721 reference to the library-based model. If you have not previously used an
1722 Ada compiler, you need only read the first part of this chapter. The
1723 last section describes and discusses the differences between the GNAT
1724 model and the traditional Ada compiler models. If you have used other
1725 Ada compilers, this section will help you to understand those
1726 differences, and the advantages of the GNAT model.
1728 @node Source Representation
1729 @section Source Representation
1733 Ada source programs are represented in standard text files, using
1734 Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar
1735 7-bit ASCII set, plus additional characters used for
1736 representing foreign languages (@pxref{Foreign Language Representation}
1737 for support of non-USA character sets). The format effector characters
1738 are represented using their standard ASCII encodings, as follows:
1743 Vertical tab, @code{16#0B#}
1747 Horizontal tab, @code{16#09#}
1751 Carriage return, @code{16#0D#}
1755 Line feed, @code{16#0A#}
1759 Form feed, @code{16#0C#}
1763 Source files are in standard text file format. In addition, GNAT will
1764 recognize a wide variety of stream formats, in which the end of
1765 physical lines is marked by any of the following sequences:
1766 @code{LF}, @code{CR}, @code{CR-LF}, or @code{LF-CR}. This is useful
1767 in accommodating files that are imported from other operating systems.
1769 @cindex End of source file
1770 @cindex Source file, end
1772 The end of a source file is normally represented by the physical end of
1773 file. However, the control character @code{16#1A#} (@code{SUB}) is also
1774 recognized as signalling the end of the source file. Again, this is
1775 provided for compatibility with other operating systems where this
1776 code is used to represent the end of file.
1778 Each file contains a single Ada compilation unit, including any pragmas
1779 associated with the unit. For example, this means you must place a
1780 package declaration (a package @dfn{spec}) and the corresponding body in
1781 separate files. An Ada @dfn{compilation} (which is a sequence of
1782 compilation units) is represented using a sequence of files. Similarly,
1783 you will place each subunit or child unit in a separate file.
1785 @node Foreign Language Representation
1786 @section Foreign Language Representation
1789 GNAT supports the standard character sets defined in Ada as well as
1790 several other non-standard character sets for use in localized versions
1791 of the compiler (@pxref{Character Set Control}).
1794 * Other 8-Bit Codes::
1795 * Wide Character Encodings::
1803 The basic character set is Latin-1. This character set is defined by ISO
1804 standard 8859, part 1. The lower half (character codes @code{16#00#}
1805 @dots{} @code{16#7F#)} is identical to standard ASCII coding, but the upper half
1806 is used to represent additional characters. These include extended letters
1807 used by European languages, such as French accents, the vowels with umlauts
1808 used in German, and the extra letter A-ring used in Swedish.
1810 @findex Ada.Characters.Latin_1
1811 For a complete list of Latin-1 codes and their encodings, see the source
1812 file of library unit @code{Ada.Characters.Latin_1} in file
1813 @file{a-chlat1.ads}.
1814 You may use any of these extended characters freely in character or
1815 string literals. In addition, the extended characters that represent
1816 letters can be used in identifiers.
1818 @node Other 8-Bit Codes
1819 @subsection Other 8-Bit Codes
1822 GNAT also supports several other 8-bit coding schemes:
1825 @item ISO 8859-2 (Latin-2)
1828 Latin-2 letters allowed in identifiers, with uppercase and lowercase
1831 @item ISO 8859-3 (Latin-3)
1834 Latin-3 letters allowed in identifiers, with uppercase and lowercase
1837 @item ISO 8859-4 (Latin-4)
1840 Latin-4 letters allowed in identifiers, with uppercase and lowercase
1843 @item ISO 8859-5 (Cyrillic)
1846 ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and
1847 lowercase equivalence.
1849 @item ISO 8859-15 (Latin-9)
1852 ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and
1853 lowercase equivalence
1855 @item IBM PC (code page 437)
1856 @cindex code page 437
1857 This code page is the normal default for PCs in the U.S. It corresponds
1858 to the original IBM PC character set. This set has some, but not all, of
1859 the extended Latin-1 letters, but these letters do not have the same
1860 encoding as Latin-1. In this mode, these letters are allowed in
1861 identifiers with uppercase and lowercase equivalence.
1863 @item IBM PC (code page 850)
1864 @cindex code page 850
1865 This code page is a modification of 437 extended to include all the
1866 Latin-1 letters, but still not with the usual Latin-1 encoding. In this
1867 mode, all these letters are allowed in identifiers with uppercase and
1868 lowercase equivalence.
1870 @item Full Upper 8-bit
1871 Any character in the range 80-FF allowed in identifiers, and all are
1872 considered distinct. In other words, there are no uppercase and lowercase
1873 equivalences in this range. This is useful in conjunction with
1874 certain encoding schemes used for some foreign character sets (e.g.,
1875 the typical method of representing Chinese characters on the PC).
1878 No upper-half characters in the range 80-FF are allowed in identifiers.
1879 This gives Ada 83 compatibility for identifier names.
1883 For precise data on the encodings permitted, and the uppercase and lowercase
1884 equivalences that are recognized, see the file @file{csets.adb} in
1885 the GNAT compiler sources. You will need to obtain a full source release
1886 of GNAT to obtain this file.
1888 @node Wide Character Encodings
1889 @subsection Wide Character Encodings
1892 GNAT allows wide character codes to appear in character and string
1893 literals, and also optionally in identifiers, by means of the following
1894 possible encoding schemes:
1899 In this encoding, a wide character is represented by the following five
1907 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1908 characters (using uppercase letters) of the wide character code. For
1909 example, ESC A345 is used to represent the wide character with code
1911 This scheme is compatible with use of the full Wide_Character set.
1913 @item Upper-Half Coding
1914 @cindex Upper-Half Coding
1915 The wide character with encoding @code{16#abcd#} where the upper bit is on
1916 (in other words, ``a'' is in the range 8-F) is represented as two bytes,
1917 @code{16#ab#} and @code{16#cd#}. The second byte cannot be a format control
1918 character, but is not required to be in the upper half. This method can
1919 be also used for shift-JIS or EUC, where the internal coding matches the
1922 @item Shift JIS Coding
1923 @cindex Shift JIS Coding
1924 A wide character is represented by a two-character sequence,
1926 @code{16#cd#}, with the restrictions described for upper-half encoding as
1927 described above. The internal character code is the corresponding JIS
1928 character according to the standard algorithm for Shift-JIS
1929 conversion. Only characters defined in the JIS code set table can be
1930 used with this encoding method.
1934 A wide character is represented by a two-character sequence
1936 @code{16#cd#}, with both characters being in the upper half. The internal
1937 character code is the corresponding JIS character according to the EUC
1938 encoding algorithm. Only characters defined in the JIS code set table
1939 can be used with this encoding method.
1942 A wide character is represented using
1943 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
1944 10646-1/Am.2. Depending on the character value, the representation
1945 is a one, two, or three byte sequence:
1950 16#0000#-16#007f#: 2#0@var{xxxxxxx}#
1951 16#0080#-16#07ff#: 2#110@var{xxxxx}# 2#10@var{xxxxxx}#
1952 16#0800#-16#ffff#: 2#1110@var{xxxx}# 2#10@var{xxxxxx}# 2#10@var{xxxxxx}#
1957 where the @var{xxx} bits correspond to the left-padded bits of the
1958 16-bit character value. Note that all lower half ASCII characters
1959 are represented as ASCII bytes and all upper half characters and
1960 other wide characters are represented as sequences of upper-half
1961 (The full UTF-8 scheme allows for encoding 31-bit characters as
1962 6-byte sequences, but in this implementation, all UTF-8 sequences
1963 of four or more bytes length will be treated as illegal).
1964 @item Brackets Coding
1965 In this encoding, a wide character is represented by the following eight
1973 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1974 characters (using uppercase letters) of the wide character code. For
1975 example, [``A345''] is used to represent the wide character with code
1976 @code{16#A345#}. It is also possible (though not required) to use the
1977 Brackets coding for upper half characters. For example, the code
1978 @code{16#A3#} can be represented as @code{[``A3'']}.
1980 This scheme is compatible with use of the full Wide_Character set,
1981 and is also the method used for wide character encoding in the standard
1982 ACVC (Ada Compiler Validation Capability) test suite distributions.
1987 Note: Some of these coding schemes do not permit the full use of the
1988 Ada character set. For example, neither Shift JIS, nor EUC allow the
1989 use of the upper half of the Latin-1 set.
1991 @node File Naming Rules
1992 @section File Naming Rules
1995 The default file name is determined by the name of the unit that the
1996 file contains. The name is formed by taking the full expanded name of
1997 the unit and replacing the separating dots with hyphens and using
1998 ^lowercase^uppercase^ for all letters.
2000 An exception arises if the file name generated by the above rules starts
2001 with one of the characters
2003 @samp{A}, @samp{G}, @samp{I}, or @samp{S},
2006 @samp{a}, @samp{g}, @samp{i}, or @samp{s},
2008 and the second character is a
2009 minus. In this case, the character ^tilde^dollar sign^ is used in place
2010 of the minus. The reason for this special rule is to avoid clashes with
2011 the standard names for child units of the packages System, Ada,
2012 Interfaces, and GNAT, which use the prefixes
2014 @samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},
2017 @samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},
2021 The file extension is @file{.ads} for a spec and
2022 @file{.adb} for a body. The following list shows some
2023 examples of these rules.
2030 @item arith_functions.ads
2031 Arith_Functions (package spec)
2032 @item arith_functions.adb
2033 Arith_Functions (package body)
2035 Func.Spec (child package spec)
2037 Func.Spec (child package body)
2039 Sub (subunit of Main)
2040 @item ^a~bad.adb^A$BAD.ADB^
2041 A.Bad (child package body)
2045 Following these rules can result in excessively long
2046 file names if corresponding
2047 unit names are long (for example, if child units or subunits are
2048 heavily nested). An option is available to shorten such long file names
2049 (called file name ``krunching''). This may be particularly useful when
2050 programs being developed with GNAT are to be used on operating systems
2051 with limited file name lengths. @xref{Using gnatkr}.
2053 Of course, no file shortening algorithm can guarantee uniqueness over
2054 all possible unit names; if file name krunching is used, it is your
2055 responsibility to ensure no name clashes occur. Alternatively you
2056 can specify the exact file names that you want used, as described
2057 in the next section. Finally, if your Ada programs are migrating from a
2058 compiler with a different naming convention, you can use the gnatchop
2059 utility to produce source files that follow the GNAT naming conventions.
2060 (For details @pxref{Renaming Files Using gnatchop}.)
2062 Note: in the case of @code{Windows NT/XP} or @code{OpenVMS} operating
2063 systems, case is not significant. So for example on @code{Windows XP}
2064 if the canonical name is @code{main-sub.adb}, you can use the file name
2065 @code{Main-Sub.adb} instead. However, case is significant for other
2066 operating systems, so for example, if you want to use other than
2067 canonically cased file names on a Unix system, you need to follow
2068 the procedures described in the next section.
2070 @node Using Other File Names
2071 @section Using Other File Names
2075 In the previous section, we have described the default rules used by
2076 GNAT to determine the file name in which a given unit resides. It is
2077 often convenient to follow these default rules, and if you follow them,
2078 the compiler knows without being explicitly told where to find all
2081 However, in some cases, particularly when a program is imported from
2082 another Ada compiler environment, it may be more convenient for the
2083 programmer to specify which file names contain which units. GNAT allows
2084 arbitrary file names to be used by means of the Source_File_Name pragma.
2085 The form of this pragma is as shown in the following examples:
2086 @cindex Source_File_Name pragma
2088 @smallexample @c ada
2090 pragma Source_File_Name (My_Utilities.Stacks,
2091 Spec_File_Name => "myutilst_a.ada");
2092 pragma Source_File_name (My_Utilities.Stacks,
2093 Body_File_Name => "myutilst.ada");
2098 As shown in this example, the first argument for the pragma is the unit
2099 name (in this example a child unit). The second argument has the form
2100 of a named association. The identifier
2101 indicates whether the file name is for a spec or a body;
2102 the file name itself is given by a string literal.
2104 The source file name pragma is a configuration pragma, which means that
2105 normally it will be placed in the @file{gnat.adc}
2106 file used to hold configuration
2107 pragmas that apply to a complete compilation environment.
2108 For more details on how the @file{gnat.adc} file is created and used
2109 see @ref{Handling of Configuration Pragmas}.
2110 @cindex @file{gnat.adc}
2113 GNAT allows completely arbitrary file names to be specified using the
2114 source file name pragma. However, if the file name specified has an
2115 extension other than @file{.ads} or @file{.adb} it is necessary to use
2116 a special syntax when compiling the file. The name in this case must be
2117 preceded by the special sequence @option{-x} followed by a space and the name
2118 of the language, here @code{ada}, as in:
2121 $ gcc -c -x ada peculiar_file_name.sim
2126 @command{gnatmake} handles non-standard file names in the usual manner (the
2127 non-standard file name for the main program is simply used as the
2128 argument to gnatmake). Note that if the extension is also non-standard,
2129 then it must be included in the @command{gnatmake} command, it may not
2132 @node Alternative File Naming Schemes
2133 @section Alternative File Naming Schemes
2134 @cindex File naming schemes, alternative
2137 In the previous section, we described the use of the @code{Source_File_Name}
2138 pragma to allow arbitrary names to be assigned to individual source files.
2139 However, this approach requires one pragma for each file, and especially in
2140 large systems can result in very long @file{gnat.adc} files, and also create
2141 a maintenance problem.
2143 GNAT also provides a facility for specifying systematic file naming schemes
2144 other than the standard default naming scheme previously described. An
2145 alternative scheme for naming is specified by the use of
2146 @code{Source_File_Name} pragmas having the following format:
2147 @cindex Source_File_Name pragma
2149 @smallexample @c ada
2150 pragma Source_File_Name (
2151 Spec_File_Name => FILE_NAME_PATTERN
2152 @r{[},Casing => CASING_SPEC@r{]}
2153 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2155 pragma Source_File_Name (
2156 Body_File_Name => FILE_NAME_PATTERN
2157 @r{[},Casing => CASING_SPEC@r{]}
2158 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2160 pragma Source_File_Name (
2161 Subunit_File_Name => FILE_NAME_PATTERN
2162 @r{[},Casing => CASING_SPEC@r{]}
2163 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2165 FILE_NAME_PATTERN ::= STRING_LITERAL
2166 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
2170 The @code{FILE_NAME_PATTERN} string shows how the file name is constructed.
2171 It contains a single asterisk character, and the unit name is substituted
2172 systematically for this asterisk. The optional parameter
2173 @code{Casing} indicates
2174 whether the unit name is to be all upper-case letters, all lower-case letters,
2175 or mixed-case. If no
2176 @code{Casing} parameter is used, then the default is all
2177 ^lower-case^upper-case^.
2179 The optional @code{Dot_Replacement} string is used to replace any periods
2180 that occur in subunit or child unit names. If no @code{Dot_Replacement}
2181 argument is used then separating dots appear unchanged in the resulting
2183 Although the above syntax indicates that the
2184 @code{Casing} argument must appear
2185 before the @code{Dot_Replacement} argument, but it
2186 is also permissible to write these arguments in the opposite order.
2188 As indicated, it is possible to specify different naming schemes for
2189 bodies, specs, and subunits. Quite often the rule for subunits is the
2190 same as the rule for bodies, in which case, there is no need to give
2191 a separate @code{Subunit_File_Name} rule, and in this case the
2192 @code{Body_File_name} rule is used for subunits as well.
2194 The separate rule for subunits can also be used to implement the rather
2195 unusual case of a compilation environment (e.g.@: a single directory) which
2196 contains a subunit and a child unit with the same unit name. Although
2197 both units cannot appear in the same partition, the Ada Reference Manual
2198 allows (but does not require) the possibility of the two units coexisting
2199 in the same environment.
2201 The file name translation works in the following steps:
2206 If there is a specific @code{Source_File_Name} pragma for the given unit,
2207 then this is always used, and any general pattern rules are ignored.
2210 If there is a pattern type @code{Source_File_Name} pragma that applies to
2211 the unit, then the resulting file name will be used if the file exists. If
2212 more than one pattern matches, the latest one will be tried first, and the
2213 first attempt resulting in a reference to a file that exists will be used.
2216 If no pattern type @code{Source_File_Name} pragma that applies to the unit
2217 for which the corresponding file exists, then the standard GNAT default
2218 naming rules are used.
2223 As an example of the use of this mechanism, consider a commonly used scheme
2224 in which file names are all lower case, with separating periods copied
2225 unchanged to the resulting file name, and specs end with @file{.1.ada}, and
2226 bodies end with @file{.2.ada}. GNAT will follow this scheme if the following
2229 @smallexample @c ada
2230 pragma Source_File_Name
2231 (Spec_File_Name => "*.1.ada");
2232 pragma Source_File_Name
2233 (Body_File_Name => "*.2.ada");
2237 The default GNAT scheme is actually implemented by providing the following
2238 default pragmas internally:
2240 @smallexample @c ada
2241 pragma Source_File_Name
2242 (Spec_File_Name => "*.ads", Dot_Replacement => "-");
2243 pragma Source_File_Name
2244 (Body_File_Name => "*.adb", Dot_Replacement => "-");
2248 Our final example implements a scheme typically used with one of the
2249 Ada 83 compilers, where the separator character for subunits was ``__''
2250 (two underscores), specs were identified by adding @file{_.ADA}, bodies
2251 by adding @file{.ADA}, and subunits by
2252 adding @file{.SEP}. All file names were
2253 upper case. Child units were not present of course since this was an
2254 Ada 83 compiler, but it seems reasonable to extend this scheme to use
2255 the same double underscore separator for child units.
2257 @smallexample @c ada
2258 pragma Source_File_Name
2259 (Spec_File_Name => "*_.ADA",
2260 Dot_Replacement => "__",
2261 Casing = Uppercase);
2262 pragma Source_File_Name
2263 (Body_File_Name => "*.ADA",
2264 Dot_Replacement => "__",
2265 Casing = Uppercase);
2266 pragma Source_File_Name
2267 (Subunit_File_Name => "*.SEP",
2268 Dot_Replacement => "__",
2269 Casing = Uppercase);
2272 @node Generating Object Files
2273 @section Generating Object Files
2276 An Ada program consists of a set of source files, and the first step in
2277 compiling the program is to generate the corresponding object files.
2278 These are generated by compiling a subset of these source files.
2279 The files you need to compile are the following:
2283 If a package spec has no body, compile the package spec to produce the
2284 object file for the package.
2287 If a package has both a spec and a body, compile the body to produce the
2288 object file for the package. The source file for the package spec need
2289 not be compiled in this case because there is only one object file, which
2290 contains the code for both the spec and body of the package.
2293 For a subprogram, compile the subprogram body to produce the object file
2294 for the subprogram. The spec, if one is present, is as usual in a
2295 separate file, and need not be compiled.
2299 In the case of subunits, only compile the parent unit. A single object
2300 file is generated for the entire subunit tree, which includes all the
2304 Compile child units independently of their parent units
2305 (though, of course, the spec of all the ancestor unit must be present in order
2306 to compile a child unit).
2310 Compile generic units in the same manner as any other units. The object
2311 files in this case are small dummy files that contain at most the
2312 flag used for elaboration checking. This is because GNAT always handles generic
2313 instantiation by means of macro expansion. However, it is still necessary to
2314 compile generic units, for dependency checking and elaboration purposes.
2318 The preceding rules describe the set of files that must be compiled to
2319 generate the object files for a program. Each object file has the same
2320 name as the corresponding source file, except that the extension is
2323 You may wish to compile other files for the purpose of checking their
2324 syntactic and semantic correctness. For example, in the case where a
2325 package has a separate spec and body, you would not normally compile the
2326 spec. However, it is convenient in practice to compile the spec to make
2327 sure it is error-free before compiling clients of this spec, because such
2328 compilations will fail if there is an error in the spec.
2330 GNAT provides an option for compiling such files purely for the
2331 purposes of checking correctness; such compilations are not required as
2332 part of the process of building a program. To compile a file in this
2333 checking mode, use the @option{-gnatc} switch.
2335 @node Source Dependencies
2336 @section Source Dependencies
2339 A given object file clearly depends on the source file which is compiled
2340 to produce it. Here we are using @dfn{depends} in the sense of a typical
2341 @code{make} utility; in other words, an object file depends on a source
2342 file if changes to the source file require the object file to be
2344 In addition to this basic dependency, a given object may depend on
2345 additional source files as follows:
2349 If a file being compiled @code{with}'s a unit @var{X}, the object file
2350 depends on the file containing the spec of unit @var{X}. This includes
2351 files that are @code{with}'ed implicitly either because they are parents
2352 of @code{with}'ed child units or they are run-time units required by the
2353 language constructs used in a particular unit.
2356 If a file being compiled instantiates a library level generic unit, the
2357 object file depends on both the spec and body files for this generic
2361 If a file being compiled instantiates a generic unit defined within a
2362 package, the object file depends on the body file for the package as
2363 well as the spec file.
2367 @cindex @option{-gnatn} switch
2368 If a file being compiled contains a call to a subprogram for which
2369 pragma @code{Inline} applies and inlining is activated with the
2370 @option{-gnatn} switch, the object file depends on the file containing the
2371 body of this subprogram as well as on the file containing the spec. Note
2372 that for inlining to actually occur as a result of the use of this switch,
2373 it is necessary to compile in optimizing mode.
2375 @cindex @option{-gnatN} switch
2376 The use of @option{-gnatN} activates inlining optimization
2377 that is performed by the front end of the compiler. This inlining does
2378 not require that the code generation be optimized. Like @option{-gnatn},
2379 the use of this switch generates additional dependencies.
2381 When using a gcc-based back end (in practice this means using any version
2382 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
2383 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
2384 Historically front end inlining was more extensive than the gcc back end
2385 inlining, but that is no longer the case.
2388 If an object file @file{O} depends on the proper body of a subunit through
2389 inlining or instantiation, it depends on the parent unit of the subunit.
2390 This means that any modification of the parent unit or one of its subunits
2391 affects the compilation of @file{O}.
2394 The object file for a parent unit depends on all its subunit body files.
2397 The previous two rules meant that for purposes of computing dependencies and
2398 recompilation, a body and all its subunits are treated as an indivisible whole.
2401 These rules are applied transitively: if unit @code{A} @code{with}'s
2402 unit @code{B}, whose elaboration calls an inlined procedure in package
2403 @code{C}, the object file for unit @code{A} will depend on the body of
2404 @code{C}, in file @file{c.adb}.
2406 The set of dependent files described by these rules includes all the
2407 files on which the unit is semantically dependent, as dictated by the
2408 Ada language standard. However, it is a superset of what the
2409 standard describes, because it includes generic, inline, and subunit
2412 An object file must be recreated by recompiling the corresponding source
2413 file if any of the source files on which it depends are modified. For
2414 example, if the @code{make} utility is used to control compilation,
2415 the rule for an Ada object file must mention all the source files on
2416 which the object file depends, according to the above definition.
2417 The determination of the necessary
2418 recompilations is done automatically when one uses @command{gnatmake}.
2421 @node The Ada Library Information Files
2422 @section The Ada Library Information Files
2423 @cindex Ada Library Information files
2424 @cindex @file{ALI} files
2427 Each compilation actually generates two output files. The first of these
2428 is the normal object file that has a @file{.o} extension. The second is a
2429 text file containing full dependency information. It has the same
2430 name as the source file, but an @file{.ali} extension.
2431 This file is known as the Ada Library Information (@file{ALI}) file.
2432 The following information is contained in the @file{ALI} file.
2436 Version information (indicates which version of GNAT was used to compile
2437 the unit(s) in question)
2440 Main program information (including priority and time slice settings,
2441 as well as the wide character encoding used during compilation).
2444 List of arguments used in the @command{gcc} command for the compilation
2447 Attributes of the unit, including configuration pragmas used, an indication
2448 of whether the compilation was successful, exception model used etc.
2451 A list of relevant restrictions applying to the unit (used for consistency)
2455 Categorization information (e.g.@: use of pragma @code{Pure}).
2458 Information on all @code{with}'ed units, including presence of
2459 @code{Elaborate} or @code{Elaborate_All} pragmas.
2462 Information from any @code{Linker_Options} pragmas used in the unit
2465 Information on the use of @code{Body_Version} or @code{Version}
2466 attributes in the unit.
2469 Dependency information. This is a list of files, together with
2470 time stamp and checksum information. These are files on which
2471 the unit depends in the sense that recompilation is required
2472 if any of these units are modified.
2475 Cross-reference data. Contains information on all entities referenced
2476 in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to
2477 provide cross-reference information.
2482 For a full detailed description of the format of the @file{ALI} file,
2483 see the source of the body of unit @code{Lib.Writ}, contained in file
2484 @file{lib-writ.adb} in the GNAT compiler sources.
2486 @node Binding an Ada Program
2487 @section Binding an Ada Program
2490 When using languages such as C and C++, once the source files have been
2491 compiled the only remaining step in building an executable program
2492 is linking the object modules together. This means that it is possible to
2493 link an inconsistent version of a program, in which two units have
2494 included different versions of the same header.
2496 The rules of Ada do not permit such an inconsistent program to be built.
2497 For example, if two clients have different versions of the same package,
2498 it is illegal to build a program containing these two clients.
2499 These rules are enforced by the GNAT binder, which also determines an
2500 elaboration order consistent with the Ada rules.
2502 The GNAT binder is run after all the object files for a program have
2503 been created. It is given the name of the main program unit, and from
2504 this it determines the set of units required by the program, by reading the
2505 corresponding ALI files. It generates error messages if the program is
2506 inconsistent or if no valid order of elaboration exists.
2508 If no errors are detected, the binder produces a main program, in Ada by
2509 default, that contains calls to the elaboration procedures of those
2510 compilation unit that require them, followed by
2511 a call to the main program. This Ada program is compiled to generate the
2512 object file for the main program. The name of
2513 the Ada file is @file{b~@var{xxx}.adb} (with the corresponding spec
2514 @file{b~@var{xxx}.ads}) where @var{xxx} is the name of the
2517 Finally, the linker is used to build the resulting executable program,
2518 using the object from the main program from the bind step as well as the
2519 object files for the Ada units of the program.
2521 @node Mixed Language Programming
2522 @section Mixed Language Programming
2523 @cindex Mixed Language Programming
2526 This section describes how to develop a mixed-language program,
2527 specifically one that comprises units in both Ada and C.
2530 * Interfacing to C::
2531 * Calling Conventions::
2534 @node Interfacing to C
2535 @subsection Interfacing to C
2537 Interfacing Ada with a foreign language such as C involves using
2538 compiler directives to import and/or export entity definitions in each
2539 language---using @code{extern} statements in C, for instance, and the
2540 @code{Import}, @code{Export}, and @code{Convention} pragmas in Ada.
2541 A full treatment of these topics is provided in Appendix B, section 1
2542 of the Ada Reference Manual.
2544 There are two ways to build a program using GNAT that contains some Ada
2545 sources and some foreign language sources, depending on whether or not
2546 the main subprogram is written in Ada. Here is a source example with
2547 the main subprogram in Ada:
2553 void print_num (int num)
2555 printf ("num is %d.\n", num);
2561 /* num_from_Ada is declared in my_main.adb */
2562 extern int num_from_Ada;
2566 return num_from_Ada;
2570 @smallexample @c ada
2572 procedure My_Main is
2574 -- Declare then export an Integer entity called num_from_Ada
2575 My_Num : Integer := 10;
2576 pragma Export (C, My_Num, "num_from_Ada");
2578 -- Declare an Ada function spec for Get_Num, then use
2579 -- C function get_num for the implementation.
2580 function Get_Num return Integer;
2581 pragma Import (C, Get_Num, "get_num");
2583 -- Declare an Ada procedure spec for Print_Num, then use
2584 -- C function print_num for the implementation.
2585 procedure Print_Num (Num : Integer);
2586 pragma Import (C, Print_Num, "print_num");
2589 Print_Num (Get_Num);
2595 To build this example, first compile the foreign language files to
2596 generate object files:
2598 ^gcc -c file1.c^gcc -c FILE1.C^
2599 ^gcc -c file2.c^gcc -c FILE2.C^
2603 Then, compile the Ada units to produce a set of object files and ALI
2606 gnatmake ^-c^/ACTIONS=COMPILE^ my_main.adb
2610 Run the Ada binder on the Ada main program:
2612 gnatbind my_main.ali
2616 Link the Ada main program, the Ada objects and the other language
2619 gnatlink my_main.ali file1.o file2.o
2623 The last three steps can be grouped in a single command:
2625 gnatmake my_main.adb -largs file1.o file2.o
2628 @cindex Binder output file
2630 If the main program is in a language other than Ada, then you may have
2631 more than one entry point into the Ada subsystem. You must use a special
2632 binder option to generate callable routines that initialize and
2633 finalize the Ada units (@pxref{Binding with Non-Ada Main Programs}).
2634 Calls to the initialization and finalization routines must be inserted
2635 in the main program, or some other appropriate point in the code. The
2636 call to initialize the Ada units must occur before the first Ada
2637 subprogram is called, and the call to finalize the Ada units must occur
2638 after the last Ada subprogram returns. The binder will place the
2639 initialization and finalization subprograms into the
2640 @file{b~@var{xxx}.adb} file where they can be accessed by your C
2641 sources. To illustrate, we have the following example:
2645 extern void adainit (void);
2646 extern void adafinal (void);
2647 extern int add (int, int);
2648 extern int sub (int, int);
2650 int main (int argc, char *argv[])
2656 /* Should print "21 + 7 = 28" */
2657 printf ("%d + %d = %d\n", a, b, add (a, b));
2658 /* Should print "21 - 7 = 14" */
2659 printf ("%d - %d = %d\n", a, b, sub (a, b));
2665 @smallexample @c ada
2668 function Add (A, B : Integer) return Integer;
2669 pragma Export (C, Add, "add");
2673 package body Unit1 is
2674 function Add (A, B : Integer) return Integer is
2682 function Sub (A, B : Integer) return Integer;
2683 pragma Export (C, Sub, "sub");
2687 package body Unit2 is
2688 function Sub (A, B : Integer) return Integer is
2697 The build procedure for this application is similar to the last
2698 example's. First, compile the foreign language files to generate object
2701 ^gcc -c main.c^gcc -c main.c^
2705 Next, compile the Ada units to produce a set of object files and ALI
2708 gnatmake ^-c^/ACTIONS=COMPILE^ unit1.adb
2709 gnatmake ^-c^/ACTIONS=COMPILE^ unit2.adb
2713 Run the Ada binder on every generated ALI file. Make sure to use the
2714 @option{-n} option to specify a foreign main program:
2716 gnatbind ^-n^/NOMAIN^ unit1.ali unit2.ali
2720 Link the Ada main program, the Ada objects and the foreign language
2721 objects. You need only list the last ALI file here:
2723 gnatlink unit2.ali main.o -o exec_file
2726 This procedure yields a binary executable called @file{exec_file}.
2730 Depending on the circumstances (for example when your non-Ada main object
2731 does not provide symbol @code{main}), you may also need to instruct the
2732 GNAT linker not to include the standard startup objects by passing the
2733 @option{^-nostartfiles^/NOSTART_FILES^} switch to @command{gnatlink}.
2735 @node Calling Conventions
2736 @subsection Calling Conventions
2737 @cindex Foreign Languages
2738 @cindex Calling Conventions
2739 GNAT follows standard calling sequence conventions and will thus interface
2740 to any other language that also follows these conventions. The following
2741 Convention identifiers are recognized by GNAT:
2744 @cindex Interfacing to Ada
2745 @cindex Other Ada compilers
2746 @cindex Convention Ada
2748 This indicates that the standard Ada calling sequence will be
2749 used and all Ada data items may be passed without any limitations in the
2750 case where GNAT is used to generate both the caller and callee. It is also
2751 possible to mix GNAT generated code and code generated by another Ada
2752 compiler. In this case, the data types should be restricted to simple
2753 cases, including primitive types. Whether complex data types can be passed
2754 depends on the situation. Probably it is safe to pass simple arrays, such
2755 as arrays of integers or floats. Records may or may not work, depending
2756 on whether both compilers lay them out identically. Complex structures
2757 involving variant records, access parameters, tasks, or protected types,
2758 are unlikely to be able to be passed.
2760 Note that in the case of GNAT running
2761 on a platform that supports HP Ada 83, a higher degree of compatibility
2762 can be guaranteed, and in particular records are layed out in an identical
2763 manner in the two compilers. Note also that if output from two different
2764 compilers is mixed, the program is responsible for dealing with elaboration
2765 issues. Probably the safest approach is to write the main program in the
2766 version of Ada other than GNAT, so that it takes care of its own elaboration
2767 requirements, and then call the GNAT-generated adainit procedure to ensure
2768 elaboration of the GNAT components. Consult the documentation of the other
2769 Ada compiler for further details on elaboration.
2771 However, it is not possible to mix the tasking run time of GNAT and
2772 HP Ada 83, All the tasking operations must either be entirely within
2773 GNAT compiled sections of the program, or entirely within HP Ada 83
2774 compiled sections of the program.
2776 @cindex Interfacing to Assembly
2777 @cindex Convention Assembler
2779 Specifies assembler as the convention. In practice this has the
2780 same effect as convention Ada (but is not equivalent in the sense of being
2781 considered the same convention).
2783 @cindex Convention Asm
2786 Equivalent to Assembler.
2788 @cindex Interfacing to COBOL
2789 @cindex Convention COBOL
2792 Data will be passed according to the conventions described
2793 in section B.4 of the Ada Reference Manual.
2796 @cindex Interfacing to C
2797 @cindex Convention C
2799 Data will be passed according to the conventions described
2800 in section B.3 of the Ada Reference Manual.
2802 A note on interfacing to a C ``varargs'' function:
2803 @findex C varargs function
2804 @cindex Interfacing to C varargs function
2805 @cindex varargs function interfaces
2809 In C, @code{varargs} allows a function to take a variable number of
2810 arguments. There is no direct equivalent in this to Ada. One
2811 approach that can be used is to create a C wrapper for each
2812 different profile and then interface to this C wrapper. For
2813 example, to print an @code{int} value using @code{printf},
2814 create a C function @code{printfi} that takes two arguments, a
2815 pointer to a string and an int, and calls @code{printf}.
2816 Then in the Ada program, use pragma @code{Import} to
2817 interface to @code{printfi}.
2820 It may work on some platforms to directly interface to
2821 a @code{varargs} function by providing a specific Ada profile
2822 for a particular call. However, this does not work on
2823 all platforms, since there is no guarantee that the
2824 calling sequence for a two argument normal C function
2825 is the same as for calling a @code{varargs} C function with
2826 the same two arguments.
2829 @cindex Convention Default
2834 @cindex Convention External
2841 @cindex Interfacing to C++
2842 @cindex Convention C++
2843 @item C_Plus_Plus (or CPP)
2844 This stands for C++. For most purposes this is identical to C.
2845 See the separate description of the specialized GNAT pragmas relating to
2846 C++ interfacing for further details.
2850 @cindex Interfacing to Fortran
2851 @cindex Convention Fortran
2853 Data will be passed according to the conventions described
2854 in section B.5 of the Ada Reference Manual.
2857 This applies to an intrinsic operation, as defined in the Ada
2858 Reference Manual. If a pragma Import (Intrinsic) applies to a subprogram,
2859 this means that the body of the subprogram is provided by the compiler itself,
2860 usually by means of an efficient code sequence, and that the user does not
2861 supply an explicit body for it. In an application program, the pragma may
2862 be applied to the following sets of names:
2866 Rotate_Left, Rotate_Right, Shift_Left, Shift_Right,
2867 Shift_Right_Arithmetic. The corresponding subprogram declaration must have
2868 two formal parameters. The
2869 first one must be a signed integer type or a modular type with a binary
2870 modulus, and the second parameter must be of type Natural.
2871 The return type must be the same as the type of the first argument. The size
2872 of this type can only be 8, 16, 32, or 64.
2875 Binary arithmetic operators: ``+'', ``-'', ``*'', ``/''
2876 The corresponding operator declaration must have parameters and result type
2877 that have the same root numeric type (for example, all three are long_float
2878 types). This simplifies the definition of operations that use type checking
2879 to perform dimensional checks:
2881 @smallexample @c ada
2882 type Distance is new Long_Float;
2883 type Time is new Long_Float;
2884 type Velocity is new Long_Float;
2885 function "/" (D : Distance; T : Time)
2887 pragma Import (Intrinsic, "/");
2891 This common idiom is often programmed with a generic definition and an
2892 explicit body. The pragma makes it simpler to introduce such declarations.
2893 It incurs no overhead in compilation time or code size, because it is
2894 implemented as a single machine instruction.
2897 General subprogram entities, to bind an Ada subprogram declaration to
2898 a compiler builtin by name with back-ends where such interfaces are
2899 available. A typical example is the set of ``__builtin'' functions
2900 exposed by the GCC back-end, as in the following example:
2902 @smallexample @c ada
2903 function builtin_sqrt (F : Float) return Float;
2904 pragma Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf");
2907 Most of the GCC builtins are accessible this way, and as for other
2908 import conventions (e.g. C), it is the user's responsibility to ensure
2909 that the Ada subprogram profile matches the underlying builtin
2917 @cindex Convention Stdcall
2919 This is relevant only to Windows XP/2000/NT implementations of GNAT,
2920 and specifies that the @code{Stdcall} calling sequence will be used,
2921 as defined by the NT API. Nevertheless, to ease building
2922 cross-platform bindings this convention will be handled as a @code{C} calling
2923 convention on non-Windows platforms.
2926 @cindex Convention DLL
2928 This is equivalent to @code{Stdcall}.
2931 @cindex Convention Win32
2933 This is equivalent to @code{Stdcall}.
2937 @cindex Convention Stubbed
2939 This is a special convention that indicates that the compiler
2940 should provide a stub body that raises @code{Program_Error}.
2944 GNAT additionally provides a useful pragma @code{Convention_Identifier}
2945 that can be used to parametrize conventions and allow additional synonyms
2946 to be specified. For example if you have legacy code in which the convention
2947 identifier Fortran77 was used for Fortran, you can use the configuration
2950 @smallexample @c ada
2951 pragma Convention_Identifier (Fortran77, Fortran);
2955 And from now on the identifier Fortran77 may be used as a convention
2956 identifier (for example in an @code{Import} pragma) with the same
2960 @node Building Mixed Ada & C++ Programs
2961 @section Building Mixed Ada and C++ Programs
2964 A programmer inexperienced with mixed-language development may find that
2965 building an application containing both Ada and C++ code can be a
2966 challenge. This section gives a few
2967 hints that should make this task easier. The first section addresses
2968 the differences between interfacing with C and interfacing with C++.
2970 looks into the delicate problem of linking the complete application from
2971 its Ada and C++ parts. The last section gives some hints on how the GNAT
2972 run-time library can be adapted in order to allow inter-language dispatching
2973 with a new C++ compiler.
2976 * Interfacing to C++::
2977 * Linking a Mixed C++ & Ada Program::
2978 * A Simple Example::
2979 * Interfacing with C++ constructors::
2980 * Interfacing with C++ at the Class Level::
2983 @node Interfacing to C++
2984 @subsection Interfacing to C++
2987 GNAT supports interfacing with the G++ compiler (or any C++ compiler
2988 generating code that is compatible with the G++ Application Binary
2989 Interface ---see http://www.codesourcery.com/archives/cxx-abi).
2992 Interfacing can be done at 3 levels: simple data, subprograms, and
2993 classes. In the first two cases, GNAT offers a specific @code{Convention
2994 C_Plus_Plus} (or @code{CPP}) that behaves exactly like @code{Convention C}.
2995 Usually, C++ mangles the names of subprograms. To generate proper mangled
2996 names automatically, see @ref{Generating Ada Bindings for C and C++ headers}).
2997 This problem can also be addressed manually in two ways:
3001 by modifying the C++ code in order to force a C convention using
3002 the @code{extern "C"} syntax.
3005 by figuring out the mangled name (using e.g. @command{nm}) and using it as the
3006 Link_Name argument of the pragma import.
3010 Interfacing at the class level can be achieved by using the GNAT specific
3011 pragmas such as @code{CPP_Constructor}. @xref{Interfacing to C++,,,
3012 gnat_rm, GNAT Reference Manual}, for additional information.
3014 @node Linking a Mixed C++ & Ada Program
3015 @subsection Linking a Mixed C++ & Ada Program
3018 Usually the linker of the C++ development system must be used to link
3019 mixed applications because most C++ systems will resolve elaboration
3020 issues (such as calling constructors on global class instances)
3021 transparently during the link phase. GNAT has been adapted to ease the
3022 use of a foreign linker for the last phase. Three cases can be
3027 Using GNAT and G++ (GNU C++ compiler) from the same GCC installation:
3028 The C++ linker can simply be called by using the C++ specific driver
3031 Note that if the C++ code uses inline functions, you will need to
3032 compile your C++ code with the @code{-fkeep-inline-functions} switch in
3033 order to provide an existing function implementation that the Ada code can
3037 $ g++ -c -fkeep-inline-functions file1.C
3038 $ g++ -c -fkeep-inline-functions file2.C
3039 $ gnatmake ada_unit -largs file1.o file2.o --LINK=g++
3043 Using GNAT and G++ from two different GCC installations: If both
3044 compilers are on the @env{PATH}, the previous method may be used. It is
3045 important to note that environment variables such as
3046 @env{C_INCLUDE_PATH}, @env{GCC_EXEC_PREFIX}, @env{BINUTILS_ROOT}, and
3047 @env{GCC_ROOT} will affect both compilers
3048 at the same time and may make one of the two compilers operate
3049 improperly if set during invocation of the wrong compiler. It is also
3050 very important that the linker uses the proper @file{libgcc.a} GCC
3051 library -- that is, the one from the C++ compiler installation. The
3052 implicit link command as suggested in the @command{gnatmake} command
3053 from the former example can be replaced by an explicit link command with
3054 the full-verbosity option in order to verify which library is used:
3057 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++
3059 If there is a problem due to interfering environment variables, it can
3060 be worked around by using an intermediate script. The following example
3061 shows the proper script to use when GNAT has not been installed at its
3062 default location and g++ has been installed at its default location:
3070 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script
3074 Using a non-GNU C++ compiler: The commands previously described can be
3075 used to insure that the C++ linker is used. Nonetheless, you need to add
3076 a few more parameters to the link command line, depending on the exception
3079 If the @code{setjmp/longjmp} exception mechanism is used, only the paths
3080 to the libgcc libraries are required:
3085 CC $* `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a`
3086 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3089 Where CC is the name of the non-GNU C++ compiler.
3091 If the @code{zero cost} exception mechanism is used, and the platform
3092 supports automatic registration of exception tables (e.g.@: Solaris or IRIX),
3093 paths to more objects are required:
3098 CC `gcc -print-file-name=crtbegin.o` $* \
3099 `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a` \
3100 `gcc -print-file-name=crtend.o`
3101 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3104 If the @code{zero cost} exception mechanism is used, and the platform
3105 doesn't support automatic registration of exception tables (e.g.@: HP-UX,
3106 Tru64 or AIX), the simple approach described above will not work and
3107 a pre-linking phase using GNAT will be necessary.
3111 Another alternative is to use the @command{gprbuild} multi-language builder
3112 which has a large knowledge base and knows how to link Ada and C++ code
3113 together automatically in most cases.
3115 @node A Simple Example
3116 @subsection A Simple Example
3118 The following example, provided as part of the GNAT examples, shows how
3119 to achieve procedural interfacing between Ada and C++ in both
3120 directions. The C++ class A has two methods. The first method is exported
3121 to Ada by the means of an extern C wrapper function. The second method
3122 calls an Ada subprogram. On the Ada side, The C++ calls are modelled by
3123 a limited record with a layout comparable to the C++ class. The Ada
3124 subprogram, in turn, calls the C++ method. So, starting from the C++
3125 main program, the process passes back and forth between the two
3129 Here are the compilation commands:
3131 $ gnatmake -c simple_cpp_interface
3134 $ gnatbind -n simple_cpp_interface
3135 $ gnatlink simple_cpp_interface -o cpp_main --LINK=g++
3136 -lstdc++ ex7.o cpp_main.o
3140 Here are the corresponding sources:
3148 void adainit (void);
3149 void adafinal (void);
3150 void method1 (A *t);
3172 class A : public Origin @{
3174 void method1 (void);
3175 void method2 (int v);
3185 extern "C" @{ void ada_method2 (A *t, int v);@}
3187 void A::method1 (void)
3190 printf ("in A::method1, a_value = %d \n",a_value);
3194 void A::method2 (int v)
3196 ada_method2 (this, v);
3197 printf ("in A::method2, a_value = %d \n",a_value);
3204 printf ("in A::A, a_value = %d \n",a_value);
3208 @smallexample @c ada
3210 package body Simple_Cpp_Interface is
3212 procedure Ada_Method2 (This : in out A; V : Integer) is
3218 end Simple_Cpp_Interface;
3221 package Simple_Cpp_Interface is
3224 Vptr : System.Address;
3228 pragma Convention (C, A);
3230 procedure Method1 (This : in out A);
3231 pragma Import (C, Method1);
3233 procedure Ada_Method2 (This : in out A; V : Integer);
3234 pragma Export (C, Ada_Method2);
3236 end Simple_Cpp_Interface;
3239 @node Interfacing with C++ constructors
3240 @subsection Interfacing with C++ constructors
3243 In order to interface with C++ constructors GNAT provides the
3244 @code{pragma CPP_Constructor} (@xref{Interfacing to C++,,,
3245 gnat_rm, GNAT Reference Manual}, for additional information).
3246 In this section we present some common uses of C++ constructors
3247 in mixed-languages programs in GNAT.
3249 Let us assume that we need to interface with the following
3257 @b{virtual} int Get_Value ();
3258 Root(); // Default constructor
3259 Root(int v); // 1st non-default constructor
3260 Root(int v, int w); // 2nd non-default constructor
3264 For this purpose we can write the following package spec (further
3265 information on how to build this spec is available in
3266 @ref{Interfacing with C++ at the Class Level} and
3267 @ref{Generating Ada Bindings for C and C++ headers}).
3269 @smallexample @c ada
3270 with Interfaces.C; use Interfaces.C;
3272 type Root is tagged limited record
3276 pragma Import (CPP, Root);
3278 function Get_Value (Obj : Root) return int;
3279 pragma Import (CPP, Get_Value);
3281 function Constructor return Root;
3282 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ev");
3284 function Constructor (v : Integer) return Root;
3285 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ei");
3287 function Constructor (v, w : Integer) return Root;
3288 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Eii");
3292 On the Ada side the constructor is represented by a function (whose
3293 name is arbitrary) that returns the classwide type corresponding to
3294 the imported C++ class. Although the constructor is described as a
3295 function, it is typically a procedure with an extra implicit argument
3296 (the object being initialized) at the implementation level. GNAT
3297 issues the appropriate call, whatever it is, to get the object
3298 properly initialized.
3300 Constructors can only appear in the following contexts:
3304 On the right side of an initialization of an object of type @var{T}.
3306 On the right side of an initialization of a record component of type @var{T}.
3308 In an Ada 2005 limited aggregate.
3310 In an Ada 2005 nested limited aggregate.
3312 In an Ada 2005 limited aggregate that initializes an object built in
3313 place by an extended return statement.
3317 In a declaration of an object whose type is a class imported from C++,
3318 either the default C++ constructor is implicitly called by GNAT, or
3319 else the required C++ constructor must be explicitly called in the
3320 expression that initializes the object. For example:
3322 @smallexample @c ada
3324 Obj2 : Root := Constructor;
3325 Obj3 : Root := Constructor (v => 10);
3326 Obj4 : Root := Constructor (30, 40);
3329 The first two declarations are equivalent: in both cases the default C++
3330 constructor is invoked (in the former case the call to the constructor is
3331 implicit, and in the latter case the call is explicit in the object
3332 declaration). @code{Obj3} is initialized by the C++ non-default constructor
3333 that takes an integer argument, and @code{Obj4} is initialized by the
3334 non-default C++ constructor that takes two integers.
3336 Let us derive the imported C++ class in the Ada side. For example:
3338 @smallexample @c ada
3339 type DT is new Root with record
3340 C_Value : Natural := 2009;
3344 In this case the components DT inherited from the C++ side must be
3345 initialized by a C++ constructor, and the additional Ada components
3346 of type DT are initialized by GNAT. The initialization of such an
3347 object is done either by default, or by means of a function returning
3348 an aggregate of type DT, or by means of an extension aggregate.
3350 @smallexample @c ada
3352 Obj6 : DT := Function_Returning_DT (50);
3353 Obj7 : DT := (Constructor (30,40) with C_Value => 50);
3356 The declaration of @code{Obj5} invokes the default constructors: the
3357 C++ default constructor of the parent type takes care of the initialization
3358 of the components inherited from Root, and GNAT takes care of the default
3359 initialization of the additional Ada components of type DT (that is,
3360 @code{C_Value} is initialized to value 2009). The order of invocation of
3361 the constructors is consistent with the order of elaboration required by
3362 Ada and C++. That is, the constructor of the parent type is always called
3363 before the constructor of the derived type.
3365 Let us now consider a record that has components whose type is imported
3366 from C++. For example:
3368 @smallexample @c ada
3369 type Rec1 is limited record
3370 Data1 : Root := Constructor (10);
3371 Value : Natural := 1000;
3374 type Rec2 (D : Integer := 20) is limited record
3376 Data2 : Root := Constructor (D, 30);
3380 The initialization of an object of type @code{Rec2} will call the
3381 non-default C++ constructors specified for the imported components.
3384 @smallexample @c ada
3388 Using Ada 2005 we can use limited aggregates to initialize an object
3389 invoking C++ constructors that differ from those specified in the type
3390 declarations. For example:
3392 @smallexample @c ada
3393 Obj9 : Rec2 := (Rec => (Data1 => Constructor (15, 16),
3398 The above declaration uses an Ada 2005 limited aggregate to
3399 initialize @code{Obj9}, and the C++ constructor that has two integer
3400 arguments is invoked to initialize the @code{Data1} component instead
3401 of the constructor specified in the declaration of type @code{Rec1}. In
3402 Ada 2005 the box in the aggregate indicates that unspecified components
3403 are initialized using the expression (if any) available in the component
3404 declaration. That is, in this case discriminant @code{D} is initialized
3405 to value @code{20}, @code{Value} is initialized to value 1000, and the
3406 non-default C++ constructor that handles two integers takes care of
3407 initializing component @code{Data2} with values @code{20,30}.
3409 In Ada 2005 we can use the extended return statement to build the Ada
3410 equivalent to C++ non-default constructors. For example:
3412 @smallexample @c ada
3413 function Constructor (V : Integer) return Rec2 is
3415 return Obj : Rec2 := (Rec => (Data1 => Constructor (V, 20),
3418 -- Further actions required for construction of
3419 -- objects of type Rec2
3425 In this example the extended return statement construct is used to
3426 build in place the returned object whose components are initialized
3427 by means of a limited aggregate. Any further action associated with
3428 the constructor can be placed inside the construct.
3430 @node Interfacing with C++ at the Class Level
3431 @subsection Interfacing with C++ at the Class Level
3433 In this section we demonstrate the GNAT features for interfacing with
3434 C++ by means of an example making use of Ada 2005 abstract interface
3435 types. This example consists of a classification of animals; classes
3436 have been used to model our main classification of animals, and
3437 interfaces provide support for the management of secondary
3438 classifications. We first demonstrate a case in which the types and
3439 constructors are defined on the C++ side and imported from the Ada
3440 side, and latter the reverse case.
3442 The root of our derivation will be the @code{Animal} class, with a
3443 single private attribute (the @code{Age} of the animal) and two public
3444 primitives to set and get the value of this attribute.
3449 @b{virtual} void Set_Age (int New_Age);
3450 @b{virtual} int Age ();
3456 Abstract interface types are defined in C++ by means of classes with pure
3457 virtual functions and no data members. In our example we will use two
3458 interfaces that provide support for the common management of @code{Carnivore}
3459 and @code{Domestic} animals:
3462 @b{class} Carnivore @{
3464 @b{virtual} int Number_Of_Teeth () = 0;
3467 @b{class} Domestic @{
3469 @b{virtual void} Set_Owner (char* Name) = 0;
3473 Using these declarations, we can now say that a @code{Dog} is an animal that is
3474 both Carnivore and Domestic, that is:
3477 @b{class} Dog : Animal, Carnivore, Domestic @{
3479 @b{virtual} int Number_Of_Teeth ();
3480 @b{virtual} void Set_Owner (char* Name);
3482 Dog(); // Constructor
3489 In the following examples we will assume that the previous declarations are
3490 located in a file named @code{animals.h}. The following package demonstrates
3491 how to import these C++ declarations from the Ada side:
3493 @smallexample @c ada
3494 with Interfaces.C.Strings; use Interfaces.C.Strings;
3496 type Carnivore is interface;
3497 pragma Convention (C_Plus_Plus, Carnivore);
3498 function Number_Of_Teeth (X : Carnivore)
3499 return Natural is abstract;
3501 type Domestic is interface;
3502 pragma Convention (C_Plus_Plus, Set_Owner);
3504 (X : in out Domestic;
3505 Name : Chars_Ptr) is abstract;
3507 type Animal is tagged record
3510 pragma Import (C_Plus_Plus, Animal);
3512 procedure Set_Age (X : in out Animal; Age : Integer);
3513 pragma Import (C_Plus_Plus, Set_Age);
3515 function Age (X : Animal) return Integer;
3516 pragma Import (C_Plus_Plus, Age);
3518 type Dog is new Animal and Carnivore and Domestic with record
3519 Tooth_Count : Natural;
3520 Owner : String (1 .. 30);
3522 pragma Import (C_Plus_Plus, Dog);
3524 function Number_Of_Teeth (A : Dog) return Integer;
3525 pragma Import (C_Plus_Plus, Number_Of_Teeth);
3527 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3528 pragma Import (C_Plus_Plus, Set_Owner);
3530 function New_Dog return Dog;
3531 pragma CPP_Constructor (New_Dog);
3532 pragma Import (CPP, New_Dog, "_ZN3DogC2Ev");
3536 Thanks to the compatibility between GNAT run-time structures and the C++ ABI,
3537 interfacing with these C++ classes is easy. The only requirement is that all
3538 the primitives and components must be declared exactly in the same order in
3541 Regarding the abstract interfaces, we must indicate to the GNAT compiler by
3542 means of a @code{pragma Convention (C_Plus_Plus)}, the convention used to pass
3543 the arguments to the called primitives will be the same as for C++. For the
3544 imported classes we use @code{pragma Import} with convention @code{C_Plus_Plus}
3545 to indicate that they have been defined on the C++ side; this is required
3546 because the dispatch table associated with these tagged types will be built
3547 in the C++ side and therefore will not contain the predefined Ada primitives
3548 which Ada would otherwise expect.
3550 As the reader can see there is no need to indicate the C++ mangled names
3551 associated with each subprogram because it is assumed that all the calls to
3552 these primitives will be dispatching calls. The only exception is the
3553 constructor, which must be registered with the compiler by means of
3554 @code{pragma CPP_Constructor} and needs to provide its associated C++
3555 mangled name because the Ada compiler generates direct calls to it.
3557 With the above packages we can now declare objects of type Dog on the Ada side
3558 and dispatch calls to the corresponding subprograms on the C++ side. We can
3559 also extend the tagged type Dog with further fields and primitives, and
3560 override some of its C++ primitives on the Ada side. For example, here we have
3561 a type derivation defined on the Ada side that inherits all the dispatching
3562 primitives of the ancestor from the C++ side.
3565 @b{with} Animals; @b{use} Animals;
3566 @b{package} Vaccinated_Animals @b{is}
3567 @b{type} Vaccinated_Dog @b{is new} Dog @b{with null record};
3568 @b{function} Vaccination_Expired (A : Vaccinated_Dog) @b{return} Boolean;
3569 @b{end} Vaccinated_Animals;
3572 It is important to note that, because of the ABI compatibility, the programmer
3573 does not need to add any further information to indicate either the object
3574 layout or the dispatch table entry associated with each dispatching operation.
3576 Now let us define all the types and constructors on the Ada side and export
3577 them to C++, using the same hierarchy of our previous example:
3579 @smallexample @c ada
3580 with Interfaces.C.Strings;
3581 use Interfaces.C.Strings;
3583 type Carnivore is interface;
3584 pragma Convention (C_Plus_Plus, Carnivore);
3585 function Number_Of_Teeth (X : Carnivore)
3586 return Natural is abstract;
3588 type Domestic is interface;
3589 pragma Convention (C_Plus_Plus, Set_Owner);
3591 (X : in out Domestic;
3592 Name : Chars_Ptr) is abstract;
3594 type Animal is tagged record
3597 pragma Convention (C_Plus_Plus, Animal);
3599 procedure Set_Age (X : in out Animal; Age : Integer);
3600 pragma Export (C_Plus_Plus, Set_Age);
3602 function Age (X : Animal) return Integer;
3603 pragma Export (C_Plus_Plus, Age);
3605 type Dog is new Animal and Carnivore and Domestic with record
3606 Tooth_Count : Natural;
3607 Owner : String (1 .. 30);
3609 pragma Convention (C_Plus_Plus, Dog);
3611 function Number_Of_Teeth (A : Dog) return Integer;
3612 pragma Export (C_Plus_Plus, Number_Of_Teeth);
3614 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3615 pragma Export (C_Plus_Plus, Set_Owner);
3617 function New_Dog return Dog'Class;
3618 pragma Export (C_Plus_Plus, New_Dog);
3622 Compared with our previous example the only difference is the use of
3623 @code{pragma Export} to indicate to the GNAT compiler that the primitives will
3624 be available to C++. Thanks to the ABI compatibility, on the C++ side there is
3625 nothing else to be done; as explained above, the only requirement is that all
3626 the primitives and components are declared in exactly the same order.
3628 For completeness, let us see a brief C++ main program that uses the
3629 declarations available in @code{animals.h} (presented in our first example) to
3630 import and use the declarations from the Ada side, properly initializing and
3631 finalizing the Ada run-time system along the way:
3634 @b{#include} "animals.h"
3635 @b{#include} <iostream>
3636 @b{using namespace} std;
3638 void Check_Carnivore (Carnivore *obj) @{@dots{}@}
3639 void Check_Domestic (Domestic *obj) @{@dots{}@}
3640 void Check_Animal (Animal *obj) @{@dots{}@}
3641 void Check_Dog (Dog *obj) @{@dots{}@}
3644 void adainit (void);
3645 void adafinal (void);
3651 Dog *obj = new_dog(); // Ada constructor
3652 Check_Carnivore (obj); // Check secondary DT
3653 Check_Domestic (obj); // Check secondary DT
3654 Check_Animal (obj); // Check primary DT
3655 Check_Dog (obj); // Check primary DT
3660 adainit (); test(); adafinal ();
3665 @node Comparison between GNAT and C/C++ Compilation Models
3666 @section Comparison between GNAT and C/C++ Compilation Models
3669 The GNAT model of compilation is close to the C and C++ models. You can
3670 think of Ada specs as corresponding to header files in C. As in C, you
3671 don't need to compile specs; they are compiled when they are used. The
3672 Ada @code{with} is similar in effect to the @code{#include} of a C
3675 One notable difference is that, in Ada, you may compile specs separately
3676 to check them for semantic and syntactic accuracy. This is not always
3677 possible with C headers because they are fragments of programs that have
3678 less specific syntactic or semantic rules.
3680 The other major difference is the requirement for running the binder,
3681 which performs two important functions. First, it checks for
3682 consistency. In C or C++, the only defense against assembling
3683 inconsistent programs lies outside the compiler, in a makefile, for
3684 example. The binder satisfies the Ada requirement that it be impossible
3685 to construct an inconsistent program when the compiler is used in normal
3688 @cindex Elaboration order control
3689 The other important function of the binder is to deal with elaboration
3690 issues. There are also elaboration issues in C++ that are handled
3691 automatically. This automatic handling has the advantage of being
3692 simpler to use, but the C++ programmer has no control over elaboration.
3693 Where @code{gnatbind} might complain there was no valid order of
3694 elaboration, a C++ compiler would simply construct a program that
3695 malfunctioned at run time.
3698 @node Comparison between GNAT and Conventional Ada Library Models
3699 @section Comparison between GNAT and Conventional Ada Library Models
3702 This section is intended for Ada programmers who have
3703 used an Ada compiler implementing the traditional Ada library
3704 model, as described in the Ada Reference Manual.
3706 @cindex GNAT library
3707 In GNAT, there is no ``library'' in the normal sense. Instead, the set of
3708 source files themselves acts as the library. Compiling Ada programs does
3709 not generate any centralized information, but rather an object file and
3710 a ALI file, which are of interest only to the binder and linker.
3711 In a traditional system, the compiler reads information not only from
3712 the source file being compiled, but also from the centralized library.
3713 This means that the effect of a compilation depends on what has been
3714 previously compiled. In particular:
3718 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3719 to the version of the unit most recently compiled into the library.
3722 Inlining is effective only if the necessary body has already been
3723 compiled into the library.
3726 Compiling a unit may obsolete other units in the library.
3730 In GNAT, compiling one unit never affects the compilation of any other
3731 units because the compiler reads only source files. Only changes to source
3732 files can affect the results of a compilation. In particular:
3736 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3737 to the source version of the unit that is currently accessible to the
3742 Inlining requires the appropriate source files for the package or
3743 subprogram bodies to be available to the compiler. Inlining is always
3744 effective, independent of the order in which units are complied.
3747 Compiling a unit never affects any other compilations. The editing of
3748 sources may cause previous compilations to be out of date if they
3749 depended on the source file being modified.
3753 The most important result of these differences is that order of compilation
3754 is never significant in GNAT. There is no situation in which one is
3755 required to do one compilation before another. What shows up as order of
3756 compilation requirements in the traditional Ada library becomes, in
3757 GNAT, simple source dependencies; in other words, there is only a set
3758 of rules saying what source files must be present when a file is
3762 @node Placement of temporary files
3763 @section Placement of temporary files
3764 @cindex Temporary files (user control over placement)
3767 GNAT creates temporary files in the directory designated by the environment
3768 variable @env{TMPDIR}.
3769 (See the HP @emph{C RTL Reference Manual} on the function @code{getenv()}
3770 for detailed information on how environment variables are resolved.
3771 For most users the easiest way to make use of this feature is to simply
3772 define @env{TMPDIR} as a job level logical name).
3773 For example, if you wish to use a Ramdisk (assuming DECRAM is installed)
3774 for compiler temporary files, then you can include something like the
3775 following command in your @file{LOGIN.COM} file:
3778 $ define/job TMPDIR "/disk$scratchram/000000/temp/"
3782 If @env{TMPDIR} is not defined, then GNAT uses the directory designated by
3783 @env{TMP}; if @env{TMP} is not defined, then GNAT uses the directory
3784 designated by @env{TEMP}.
3785 If none of these environment variables are defined then GNAT uses the
3786 directory designated by the logical name @code{SYS$SCRATCH:}
3787 (by default the user's home directory). If all else fails
3788 GNAT uses the current directory for temporary files.
3791 @c *************************
3792 @node Compiling Using gcc
3793 @chapter Compiling Using @command{gcc}
3796 This chapter discusses how to compile Ada programs using the @command{gcc}
3797 command. It also describes the set of switches
3798 that can be used to control the behavior of the compiler.
3800 * Compiling Programs::
3801 * Switches for gcc::
3802 * Search Paths and the Run-Time Library (RTL)::
3803 * Order of Compilation Issues::
3807 @node Compiling Programs
3808 @section Compiling Programs
3811 The first step in creating an executable program is to compile the units
3812 of the program using the @command{gcc} command. You must compile the
3817 the body file (@file{.adb}) for a library level subprogram or generic
3821 the spec file (@file{.ads}) for a library level package or generic
3822 package that has no body
3825 the body file (@file{.adb}) for a library level package
3826 or generic package that has a body
3831 You need @emph{not} compile the following files
3836 the spec of a library unit which has a body
3843 because they are compiled as part of compiling related units. GNAT
3845 when the corresponding body is compiled, and subunits when the parent is
3848 @cindex cannot generate code
3849 If you attempt to compile any of these files, you will get one of the
3850 following error messages (where @var{fff} is the name of the file you compiled):
3853 cannot generate code for file @var{fff} (package spec)
3854 to check package spec, use -gnatc
3856 cannot generate code for file @var{fff} (missing subunits)
3857 to check parent unit, use -gnatc
3859 cannot generate code for file @var{fff} (subprogram spec)
3860 to check subprogram spec, use -gnatc
3862 cannot generate code for file @var{fff} (subunit)
3863 to check subunit, use -gnatc
3867 As indicated by the above error messages, if you want to submit
3868 one of these files to the compiler to check for correct semantics
3869 without generating code, then use the @option{-gnatc} switch.
3871 The basic command for compiling a file containing an Ada unit is
3874 $ gcc -c @ovar{switches} @file{file name}
3878 where @var{file name} is the name of the Ada file (usually
3880 @file{.ads} for a spec or @file{.adb} for a body).
3883 @option{-c} switch to tell @command{gcc} to compile, but not link, the file.
3885 The result of a successful compilation is an object file, which has the
3886 same name as the source file but an extension of @file{.o} and an Ada
3887 Library Information (ALI) file, which also has the same name as the
3888 source file, but with @file{.ali} as the extension. GNAT creates these
3889 two output files in the current directory, but you may specify a source
3890 file in any directory using an absolute or relative path specification
3891 containing the directory information.
3894 @command{gcc} is actually a driver program that looks at the extensions of
3895 the file arguments and loads the appropriate compiler. For example, the
3896 GNU C compiler is @file{cc1}, and the Ada compiler is @file{gnat1}.
3897 These programs are in directories known to the driver program (in some
3898 configurations via environment variables you set), but need not be in
3899 your path. The @command{gcc} driver also calls the assembler and any other
3900 utilities needed to complete the generation of the required object
3903 It is possible to supply several file names on the same @command{gcc}
3904 command. This causes @command{gcc} to call the appropriate compiler for
3905 each file. For example, the following command lists three separate
3906 files to be compiled:
3909 $ gcc -c x.adb y.adb z.c
3913 calls @code{gnat1} (the Ada compiler) twice to compile @file{x.adb} and
3914 @file{y.adb}, and @code{cc1} (the C compiler) once to compile @file{z.c}.
3915 The compiler generates three object files @file{x.o}, @file{y.o} and
3916 @file{z.o} and the two ALI files @file{x.ali} and @file{y.ali} from the
3917 Ada compilations. Any switches apply to all the files ^listed,^listed.^
3920 @option{-gnat@var{x}} switches, which apply only to Ada compilations.
3923 @node Switches for gcc
3924 @section Switches for @command{gcc}
3927 The @command{gcc} command accepts switches that control the
3928 compilation process. These switches are fully described in this section.
3929 First we briefly list all the switches, in alphabetical order, then we
3930 describe the switches in more detail in functionally grouped sections.
3932 More switches exist for GCC than those documented here, especially
3933 for specific targets. However, their use is not recommended as
3934 they may change code generation in ways that are incompatible with
3935 the Ada run-time library, or can cause inconsistencies between
3939 * Output and Error Message Control::
3940 * Warning Message Control::
3941 * Debugging and Assertion Control::
3942 * Validity Checking::
3945 * Using gcc for Syntax Checking::
3946 * Using gcc for Semantic Checking::
3947 * Compiling Different Versions of Ada::
3948 * Character Set Control::
3949 * File Naming Control::
3950 * Subprogram Inlining Control::
3951 * Auxiliary Output Control::
3952 * Debugging Control::
3953 * Exception Handling Control::
3954 * Units to Sources Mapping Files::
3955 * Integrated Preprocessing::
3956 * Code Generation Control::
3965 @cindex @option{-b} (@command{gcc})
3966 @item -b @var{target}
3967 Compile your program to run on @var{target}, which is the name of a
3968 system configuration. You must have a GNAT cross-compiler built if
3969 @var{target} is not the same as your host system.
3972 @cindex @option{-B} (@command{gcc})
3973 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
3974 from @var{dir} instead of the default location. Only use this switch
3975 when multiple versions of the GNAT compiler are available.
3976 @xref{Directory Options,, Options for Directory Search, gcc, Using the
3977 GNU Compiler Collection (GCC)}, for further details. You would normally
3978 use the @option{-b} or @option{-V} switch instead.
3981 @cindex @option{-c} (@command{gcc})
3982 Compile. Always use this switch when compiling Ada programs.
3984 Note: for some other languages when using @command{gcc}, notably in
3985 the case of C and C++, it is possible to use
3986 use @command{gcc} without a @option{-c} switch to
3987 compile and link in one step. In the case of GNAT, you
3988 cannot use this approach, because the binder must be run
3989 and @command{gcc} cannot be used to run the GNAT binder.
3993 @cindex @option{-fno-inline} (@command{gcc})
3994 Suppresses all back-end inlining, even if other optimization or inlining
3996 This includes suppression of inlining that results
3997 from the use of the pragma @code{Inline_Always}.
3998 Any occurrences of pragma @code{Inline} or @code{Inline_Always}
3999 are ignored, and @option{-gnatn} and @option{-gnatN} have no
4000 effect if this switch is present.
4002 @item -fno-inline-functions
4003 @cindex @option{-fno-inline-functions} (@command{gcc})
4004 Suppresses automatic inlining of simple subprograms, which is enabled
4005 if @option{-O3} is used.
4007 @item -fno-inline-small-functions
4008 @cindex @option{-fno-inline-small-functions} (@command{gcc})
4009 Suppresses automatic inlining of small subprograms, which is enabled
4010 if @option{-O2} is used.
4012 @item -fno-inline-functions-called-once
4013 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
4014 Suppresses inlining of subprograms local to the unit and called once
4015 from within it, which is enabled if @option{-O1} is used.
4018 @cindex @option{-fno-ivopts} (@command{gcc})
4019 Suppresses high-level loop induction variable optimizations, which are
4020 enabled if @option{-O1} is used. These optimizations are generally
4021 profitable but, for some specific cases of loops with numerous uses
4022 of the iteration variable that follow a common pattern, they may end
4023 up destroying the regularity that could be exploited at a lower level
4024 and thus producing inferior code.
4026 @item -fno-strict-aliasing
4027 @cindex @option{-fno-strict-aliasing} (@command{gcc})
4028 Causes the compiler to avoid assumptions regarding non-aliasing
4029 of objects of different types. See
4030 @ref{Optimization and Strict Aliasing} for details.
4033 @cindex @option{-fstack-check} (@command{gcc})
4034 Activates stack checking.
4035 See @ref{Stack Overflow Checking} for details.
4038 @cindex @option{-fstack-usage} (@command{gcc})
4039 Makes the compiler output stack usage information for the program, on a
4040 per-function basis. See @ref{Static Stack Usage Analysis} for details.
4042 @item -fcallgraph-info@r{[}=su@r{]}
4043 @cindex @option{-fcallgraph-info} (@command{gcc})
4044 Makes the compiler output callgraph information for the program, on a
4045 per-file basis. The information is generated in the VCG format. It can
4046 be decorated with stack-usage per-node information.
4049 @cindex @option{^-g^/DEBUG^} (@command{gcc})
4050 Generate debugging information. This information is stored in the object
4051 file and copied from there to the final executable file by the linker,
4052 where it can be read by the debugger. You must use the
4053 @option{^-g^/DEBUG^} switch if you plan on using the debugger.
4056 @cindex @option{-gnat83} (@command{gcc})
4057 Enforce Ada 83 restrictions.
4060 @cindex @option{-gnat95} (@command{gcc})
4061 Enforce Ada 95 restrictions.
4064 @cindex @option{-gnat05} (@command{gcc})
4065 Allow full Ada 2005 features.
4068 @cindex @option{-gnata} (@command{gcc})
4069 Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be
4070 activated. Note that these pragmas can also be controlled using the
4071 configuration pragmas @code{Assertion_Policy} and @code{Debug_Policy}.
4072 It also activates pragmas @code{Check}, @code{Precondition}, and
4073 @code{Postcondition}. Note that these pragmas can also be controlled
4074 using the configuration pragma @code{Check_Policy}.
4077 @cindex @option{-gnatA} (@command{gcc})
4078 Avoid processing @file{gnat.adc}. If a @file{gnat.adc} file is present,
4082 @cindex @option{-gnatb} (@command{gcc})
4083 Generate brief messages to @file{stderr} even if verbose mode set.
4086 @cindex @option{-gnatB} (@command{gcc})
4087 Assume no invalid (bad) values except for 'Valid attribute use
4088 (@pxref{Validity Checking}).
4091 @cindex @option{-gnatc} (@command{gcc})
4092 Check syntax and semantics only (no code generation attempted).
4095 @cindex @option{-gnatC} (@command{gcc})
4096 Generate CodePeer information (no code generation attempted).
4097 This switch will generate an intermediate representation suitable for
4098 use by CodePeer (@file{.scil} files). This switch is not compatible with
4099 code generation (it will, among other things, disable some switches such
4100 as -gnatn, and enable others such as -gnata).
4103 @cindex @option{-gnatd} (@command{gcc})
4104 Specify debug options for the compiler. The string of characters after
4105 the @option{-gnatd} specify the specific debug options. The possible
4106 characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
4107 compiler source file @file{debug.adb} for details of the implemented
4108 debug options. Certain debug options are relevant to applications
4109 programmers, and these are documented at appropriate points in this
4114 @cindex @option{-gnatD[nn]} (@command{gcc})
4117 @item /XDEBUG /LXDEBUG=nnn
4119 Create expanded source files for source level debugging. This switch
4120 also suppress generation of cross-reference information
4121 (see @option{-gnatx}).
4123 @item -gnatec=@var{path}
4124 @cindex @option{-gnatec} (@command{gcc})
4125 Specify a configuration pragma file
4127 (the equal sign is optional)
4129 (@pxref{The Configuration Pragmas Files}).
4131 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=@var{value}@r{]}
4132 @cindex @option{-gnateD} (@command{gcc})
4133 Defines a symbol, associated with @var{value}, for preprocessing.
4134 (@pxref{Integrated Preprocessing}).
4137 @cindex @option{-gnatef} (@command{gcc})
4138 Display full source path name in brief error messages.
4141 @cindex @option{-gnateG} (@command{gcc})
4142 Save result of preprocessing in a text file.
4144 @item -gnatem=@var{path}
4145 @cindex @option{-gnatem} (@command{gcc})
4146 Specify a mapping file
4148 (the equal sign is optional)
4150 (@pxref{Units to Sources Mapping Files}).
4152 @item -gnatep=@var{file}
4153 @cindex @option{-gnatep} (@command{gcc})
4154 Specify a preprocessing data file
4156 (the equal sign is optional)
4158 (@pxref{Integrated Preprocessing}).
4161 @cindex @option{-gnateS} (@command{gcc})
4162 Generate SCO (Source Coverage Obligation) information in the ALI
4163 file. This information is used by advanced coverage tools. See
4164 unit @file{SCOs} in the compiler sources for details in files
4165 @file{scos.ads} and @file{scos.adb}.
4168 @cindex @option{-gnatE} (@command{gcc})
4169 Full dynamic elaboration checks.
4172 @cindex @option{-gnatf} (@command{gcc})
4173 Full errors. Multiple errors per line, all undefined references, do not
4174 attempt to suppress cascaded errors.
4177 @cindex @option{-gnatF} (@command{gcc})
4178 Externals names are folded to all uppercase.
4180 @item ^-gnatg^/GNAT_INTERNAL^
4181 @cindex @option{^-gnatg^/GNAT_INTERNAL^} (@command{gcc})
4182 Internal GNAT implementation mode. This should not be used for
4183 applications programs, it is intended only for use by the compiler
4184 and its run-time library. For documentation, see the GNAT sources.
4185 Note that @option{^-gnatg^/GNAT_INTERNAL^} implies
4186 @option{^-gnatwae^/WARNINGS=ALL,ERRORS^} and
4187 @option{^-gnatyg^/STYLE_CHECKS=GNAT^}
4188 so that all standard warnings and all standard style options are turned on.
4189 All warnings and style error messages are treated as errors.
4193 @cindex @option{-gnatG[nn]} (@command{gcc})
4196 @item /EXPAND_SOURCE, /LEXPAND_SOURCE=nnn
4198 List generated expanded code in source form.
4200 @item ^-gnath^/HELP^
4201 @cindex @option{^-gnath^/HELP^} (@command{gcc})
4202 Output usage information. The output is written to @file{stdout}.
4204 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
4205 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
4206 Identifier character set
4208 (@var{c}=1/2/3/4/8/9/p/f/n/w).
4210 For details of the possible selections for @var{c},
4211 see @ref{Character Set Control}.
4213 @item ^-gnatI^/IGNORE_REP_CLAUSES^
4214 @cindex @option{^-gnatI^IGNORE_REP_CLAUSES^} (@command{gcc})
4215 Ignore representation clauses. When this switch is used,
4216 representation clauses are treated as comments. This is useful
4217 when initially porting code where you want to ignore rep clause
4218 problems, and also for compiling foreign code (particularly
4219 for use with ASIS). The representation clauses that are ignored
4220 are: enumeration_representation_clause, record_representation_clause,
4221 and attribute_definition_clause for the following attributes:
4222 Address, Alignment, Bit_Order, Component_Size, Machine_Radix,
4223 Object_Size, Size, Small, Stream_Size, and Value_Size.
4224 Note that this option should be used only for compiling -- the
4225 code is likely to malfunction at run time.
4228 @cindex @option{-gnatjnn} (@command{gcc})
4229 Reformat error messages to fit on nn character lines
4231 @item -gnatk=@var{n}
4232 @cindex @option{-gnatk} (@command{gcc})
4233 Limit file names to @var{n} (1-999) characters ^(@code{k} = krunch)^^.
4236 @cindex @option{-gnatl} (@command{gcc})
4237 Output full source listing with embedded error messages.
4240 @cindex @option{-gnatL} (@command{gcc})
4241 Used in conjunction with -gnatG or -gnatD to intersperse original
4242 source lines (as comment lines with line numbers) in the expanded
4245 @item -gnatm=@var{n}
4246 @cindex @option{-gnatm} (@command{gcc})
4247 Limit number of detected error or warning messages to @var{n}
4248 where @var{n} is in the range 1..999999. The default setting if
4249 no switch is given is 9999. If the number of warnings reaches this
4250 limit, then a message is output and further warnings are suppressed,
4251 but the compilation is continued. If the number of error messages
4252 reaches this limit, then a message is output and the compilation
4253 is abandoned. The equal sign here is optional. A value of zero
4254 means that no limit applies.
4257 @cindex @option{-gnatn} (@command{gcc})
4258 Activate inlining for subprograms for which
4259 pragma @code{inline} is specified. This inlining is performed
4260 by the GCC back-end.
4263 @cindex @option{-gnatN} (@command{gcc})
4264 Activate front end inlining for subprograms for which
4265 pragma @code{Inline} is specified. This inlining is performed
4266 by the front end and will be visible in the
4267 @option{-gnatG} output.
4269 When using a gcc-based back end (in practice this means using any version
4270 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
4271 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
4272 Historically front end inlining was more extensive than the gcc back end
4273 inlining, but that is no longer the case.
4276 @cindex @option{-gnato} (@command{gcc})
4277 Enable numeric overflow checking (which is not normally enabled by
4278 default). Note that division by zero is a separate check that is not
4279 controlled by this switch (division by zero checking is on by default).
4282 @cindex @option{-gnatp} (@command{gcc})
4283 Suppress all checks. See @ref{Run-Time Checks} for details.
4286 @cindex @option{-gnatP} (@command{gcc})
4287 Enable polling. This is required on some systems (notably Windows NT) to
4288 obtain asynchronous abort and asynchronous transfer of control capability.
4289 @xref{Pragma Polling,,, gnat_rm, GNAT Reference Manual}, for full
4293 @cindex @option{-gnatq} (@command{gcc})
4294 Don't quit. Try semantics, even if parse errors.
4297 @cindex @option{-gnatQ} (@command{gcc})
4298 Don't quit. Generate @file{ALI} and tree files even if illegalities.
4301 @cindex @option{-gnatr} (@command{gcc})
4302 Treat pragma Restrictions as Restriction_Warnings.
4304 @item ^-gnatR@r{[}0@r{/}1@r{/}2@r{/}3@r{[}s@r{]]}^/REPRESENTATION_INFO^
4305 @cindex @option{-gnatR} (@command{gcc})
4306 Output representation information for declared types and objects.
4309 @cindex @option{-gnats} (@command{gcc})
4313 @cindex @option{-gnatS} (@command{gcc})
4314 Print package Standard.
4317 @cindex @option{-gnatt} (@command{gcc})
4318 Generate tree output file.
4320 @item ^-gnatT^/TABLE_MULTIPLIER=^@var{nnn}
4321 @cindex @option{^-gnatT^/TABLE_MULTIPLIER^} (@command{gcc})
4322 All compiler tables start at @var{nnn} times usual starting size.
4325 @cindex @option{-gnatu} (@command{gcc})
4326 List units for this compilation.
4329 @cindex @option{-gnatU} (@command{gcc})
4330 Tag all error messages with the unique string ``error:''
4333 @cindex @option{-gnatv} (@command{gcc})
4334 Verbose mode. Full error output with source lines to @file{stdout}.
4337 @cindex @option{-gnatV} (@command{gcc})
4338 Control level of validity checking (@pxref{Validity Checking}).
4340 @item ^-gnatw@var{xxx}^/WARNINGS=(@var{option}@r{[},@dots{}@r{]})^
4341 @cindex @option{^-gnatw^/WARNINGS^} (@command{gcc})
4343 ^@var{xxx} is a string of option letters that^the list of options^ denotes
4344 the exact warnings that
4345 are enabled or disabled (@pxref{Warning Message Control}).
4347 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
4348 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
4349 Wide character encoding method
4351 (@var{e}=n/h/u/s/e/8).
4354 (@var{e}=@code{BRACKETS, NONE, HEX, UPPER, SHIFT_JIS, EUC, UTF8})
4358 @cindex @option{-gnatx} (@command{gcc})
4359 Suppress generation of cross-reference information.
4361 @item ^-gnaty^/STYLE_CHECKS=(option,option@dots{})^
4362 @cindex @option{^-gnaty^/STYLE_CHECKS^} (@command{gcc})
4363 Enable built-in style checks (@pxref{Style Checking}).
4365 @item ^-gnatz^/DISTRIBUTION_STUBS=^@var{m}
4366 @cindex @option{^-gnatz^/DISTRIBUTION_STUBS^} (@command{gcc})
4367 Distribution stub generation and compilation
4369 (@var{m}=r/c for receiver/caller stubs).
4372 (@var{m}=@code{RECEIVER} or @code{CALLER} to specify the type of stubs
4373 to be generated and compiled).
4376 @item ^-I^/SEARCH=^@var{dir}
4377 @cindex @option{^-I^/SEARCH^} (@command{gcc})
4379 Direct GNAT to search the @var{dir} directory for source files needed by
4380 the current compilation
4381 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4383 @item ^-I-^/NOCURRENT_DIRECTORY^
4384 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gcc})
4386 Except for the source file named in the command line, do not look for source
4387 files in the directory containing the source file named in the command line
4388 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4392 @cindex @option{-mbig-switch} (@command{gcc})
4393 @cindex @code{case} statement (effect of @option{-mbig-switch} option)
4394 This standard gcc switch causes the compiler to use larger offsets in its
4395 jump table representation for @code{case} statements.
4396 This may result in less efficient code, but is sometimes necessary
4397 (for example on HP-UX targets)
4398 @cindex HP-UX and @option{-mbig-switch} option
4399 in order to compile large and/or nested @code{case} statements.
4402 @cindex @option{-o} (@command{gcc})
4403 This switch is used in @command{gcc} to redirect the generated object file
4404 and its associated ALI file. Beware of this switch with GNAT, because it may
4405 cause the object file and ALI file to have different names which in turn
4406 may confuse the binder and the linker.
4410 @cindex @option{-nostdinc} (@command{gcc})
4411 Inhibit the search of the default location for the GNAT Run Time
4412 Library (RTL) source files.
4415 @cindex @option{-nostdlib} (@command{gcc})
4416 Inhibit the search of the default location for the GNAT Run Time
4417 Library (RTL) ALI files.
4421 @cindex @option{-O} (@command{gcc})
4422 @var{n} controls the optimization level.
4426 No optimization, the default setting if no @option{-O} appears
4429 Normal optimization, the default if you specify @option{-O} without
4430 an operand. A good compromise between code quality and compilation
4434 Extensive optimization, may improve execution time, possibly at the cost of
4435 substantially increased compilation time.
4438 Same as @option{-O2}, and also includes inline expansion for small subprograms
4442 Optimize space usage
4446 See also @ref{Optimization Levels}.
4451 @cindex @option{/NOOPTIMIZE} (@code{GNAT COMPILE})
4452 Equivalent to @option{/OPTIMIZE=NONE}.
4453 This is the default behavior in the absence of an @option{/OPTIMIZE}
4456 @item /OPTIMIZE@r{[}=(keyword@r{[},@dots{}@r{]})@r{]}
4457 @cindex @option{/OPTIMIZE} (@code{GNAT COMPILE})
4458 Selects the level of optimization for your program. The supported
4459 keywords are as follows:
4462 Perform most optimizations, including those that
4464 This is the default if the @option{/OPTIMIZE} qualifier is supplied
4465 without keyword options.
4468 Do not do any optimizations. Same as @code{/NOOPTIMIZE}.
4471 Perform some optimizations, but omit ones that are costly.
4474 Same as @code{SOME}.
4477 Full optimization as in @option{/OPTIMIZE=ALL}, and also attempts
4478 automatic inlining of small subprograms within a unit
4481 Try to unroll loops. This keyword may be specified together with
4482 any keyword above other than @code{NONE}. Loop unrolling
4483 usually, but not always, improves the performance of programs.
4486 Optimize space usage
4490 See also @ref{Optimization Levels}.
4494 @item -pass-exit-codes
4495 @cindex @option{-pass-exit-codes} (@command{gcc})
4496 Catch exit codes from the compiler and use the most meaningful as
4500 @item --RTS=@var{rts-path}
4501 @cindex @option{--RTS} (@command{gcc})
4502 Specifies the default location of the runtime library. Same meaning as the
4503 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
4506 @cindex @option{^-S^/ASM^} (@command{gcc})
4507 ^Used in place of @option{-c} to^Used to^
4508 cause the assembler source file to be
4509 generated, using @file{^.s^.S^} as the extension,
4510 instead of the object file.
4511 This may be useful if you need to examine the generated assembly code.
4513 @item ^-fverbose-asm^/VERBOSE_ASM^
4514 @cindex @option{^-fverbose-asm^/VERBOSE_ASM^} (@command{gcc})
4515 ^Used in conjunction with @option{-S}^Used in place of @option{/ASM}^
4516 to cause the generated assembly code file to be annotated with variable
4517 names, making it significantly easier to follow.
4520 @cindex @option{^-v^/VERBOSE^} (@command{gcc})
4521 Show commands generated by the @command{gcc} driver. Normally used only for
4522 debugging purposes or if you need to be sure what version of the
4523 compiler you are executing.
4527 @cindex @option{-V} (@command{gcc})
4528 Execute @var{ver} version of the compiler. This is the @command{gcc}
4529 version, not the GNAT version.
4532 @item ^-w^/NO_BACK_END_WARNINGS^
4533 @cindex @option{-w} (@command{gcc})
4534 Turn off warnings generated by the back end of the compiler. Use of
4535 this switch also causes the default for front end warnings to be set
4536 to suppress (as though @option{-gnatws} had appeared at the start of
4542 @c Combining qualifiers does not work on VMS
4543 You may combine a sequence of GNAT switches into a single switch. For
4544 example, the combined switch
4546 @cindex Combining GNAT switches
4552 is equivalent to specifying the following sequence of switches:
4555 -gnato -gnatf -gnati3
4560 The following restrictions apply to the combination of switches
4565 The switch @option{-gnatc} if combined with other switches must come
4566 first in the string.
4569 The switch @option{-gnats} if combined with other switches must come
4570 first in the string.
4574 @option{^-gnatz^/DISTRIBUTION_STUBS^}, @option{-gnatzc}, and @option{-gnatzr}
4575 may not be combined with any other switches.
4579 Once a ``y'' appears in the string (that is a use of the @option{-gnaty}
4580 switch), then all further characters in the switch are interpreted
4581 as style modifiers (see description of @option{-gnaty}).
4584 Once a ``d'' appears in the string (that is a use of the @option{-gnatd}
4585 switch), then all further characters in the switch are interpreted
4586 as debug flags (see description of @option{-gnatd}).
4589 Once a ``w'' appears in the string (that is a use of the @option{-gnatw}
4590 switch), then all further characters in the switch are interpreted
4591 as warning mode modifiers (see description of @option{-gnatw}).
4594 Once a ``V'' appears in the string (that is a use of the @option{-gnatV}
4595 switch), then all further characters in the switch are interpreted
4596 as validity checking options (@pxref{Validity Checking}).
4600 @node Output and Error Message Control
4601 @subsection Output and Error Message Control
4605 The standard default format for error messages is called ``brief format''.
4606 Brief format messages are written to @file{stderr} (the standard error
4607 file) and have the following form:
4610 e.adb:3:04: Incorrect spelling of keyword "function"
4611 e.adb:4:20: ";" should be "is"
4615 The first integer after the file name is the line number in the file,
4616 and the second integer is the column number within the line.
4618 @code{GPS} can parse the error messages
4619 and point to the referenced character.
4621 The following switches provide control over the error message
4627 @cindex @option{-gnatv} (@command{gcc})
4630 The v stands for verbose.
4632 The effect of this setting is to write long-format error
4633 messages to @file{stdout} (the standard output file.
4634 The same program compiled with the
4635 @option{-gnatv} switch would generate:
4639 3. funcion X (Q : Integer)
4641 >>> Incorrect spelling of keyword "function"
4644 >>> ";" should be "is"
4649 The vertical bar indicates the location of the error, and the @samp{>>>}
4650 prefix can be used to search for error messages. When this switch is
4651 used the only source lines output are those with errors.
4654 @cindex @option{-gnatl} (@command{gcc})
4656 The @code{l} stands for list.
4658 This switch causes a full listing of
4659 the file to be generated. In the case where a body is
4660 compiled, the corresponding spec is also listed, along
4661 with any subunits. Typical output from compiling a package
4662 body @file{p.adb} might look like:
4664 @smallexample @c ada
4668 1. package body p is
4670 3. procedure a is separate;
4681 2. pragma Elaborate_Body
4705 When you specify the @option{-gnatv} or @option{-gnatl} switches and
4706 standard output is redirected, a brief summary is written to
4707 @file{stderr} (standard error) giving the number of error messages and
4708 warning messages generated.
4710 @item -^gnatl^OUTPUT_FILE^=file
4711 @cindex @option{^-gnatl^OUTPUT_FILE^=fname} (@command{gcc})
4712 This has the same effect as @option{-gnatl} except that the output is
4713 written to a file instead of to standard output. If the given name
4714 @file{fname} does not start with a period, then it is the full name
4715 of the file to be written. If @file{fname} is an extension, it is
4716 appended to the name of the file being compiled. For example, if
4717 file @file{xyz.adb} is compiled with @option{^-gnatl^OUTPUT_FILE^=.lst},
4718 then the output is written to file ^xyz.adb.lst^xyz.adb_lst^.
4721 @cindex @option{-gnatU} (@command{gcc})
4722 This switch forces all error messages to be preceded by the unique
4723 string ``error:''. This means that error messages take a few more
4724 characters in space, but allows easy searching for and identification
4728 @cindex @option{-gnatb} (@command{gcc})
4730 The @code{b} stands for brief.
4732 This switch causes GNAT to generate the
4733 brief format error messages to @file{stderr} (the standard error
4734 file) as well as the verbose
4735 format message or full listing (which as usual is written to
4736 @file{stdout} (the standard output file).
4738 @item -gnatm=@var{n}
4739 @cindex @option{-gnatm} (@command{gcc})
4741 The @code{m} stands for maximum.
4743 @var{n} is a decimal integer in the
4744 range of 1 to 999999 and limits the number of error or warning
4745 messages to be generated. For example, using
4746 @option{-gnatm2} might yield
4749 e.adb:3:04: Incorrect spelling of keyword "function"
4750 e.adb:5:35: missing ".."
4751 fatal error: maximum number of errors detected
4752 compilation abandoned
4756 The default setting if
4757 no switch is given is 9999. If the number of warnings reaches this
4758 limit, then a message is output and further warnings are suppressed,
4759 but the compilation is continued. If the number of error messages
4760 reaches this limit, then a message is output and the compilation
4761 is abandoned. A value of zero means that no limit applies.
4764 Note that the equal sign is optional, so the switches
4765 @option{-gnatm2} and @option{-gnatm=2} are equivalent.
4768 @cindex @option{-gnatf} (@command{gcc})
4769 @cindex Error messages, suppressing
4771 The @code{f} stands for full.
4773 Normally, the compiler suppresses error messages that are likely to be
4774 redundant. This switch causes all error
4775 messages to be generated. In particular, in the case of
4776 references to undefined variables. If a given variable is referenced
4777 several times, the normal format of messages is
4779 e.adb:7:07: "V" is undefined (more references follow)
4783 where the parenthetical comment warns that there are additional
4784 references to the variable @code{V}. Compiling the same program with the
4785 @option{-gnatf} switch yields
4788 e.adb:7:07: "V" is undefined
4789 e.adb:8:07: "V" is undefined
4790 e.adb:8:12: "V" is undefined
4791 e.adb:8:16: "V" is undefined
4792 e.adb:9:07: "V" is undefined
4793 e.adb:9:12: "V" is undefined
4797 The @option{-gnatf} switch also generates additional information for
4798 some error messages. Some examples are:
4802 Details on possibly non-portable unchecked conversion
4804 List possible interpretations for ambiguous calls
4806 Additional details on incorrect parameters
4810 @cindex @option{-gnatjnn} (@command{gcc})
4811 In normal operation mode (or if @option{-gnatj0} is used, then error messages
4812 with continuation lines are treated as though the continuation lines were
4813 separate messages (and so a warning with two continuation lines counts as
4814 three warnings, and is listed as three separate messages).
4816 If the @option{-gnatjnn} switch is used with a positive value for nn, then
4817 messages are output in a different manner. A message and all its continuation
4818 lines are treated as a unit, and count as only one warning or message in the
4819 statistics totals. Furthermore, the message is reformatted so that no line
4820 is longer than nn characters.
4823 @cindex @option{-gnatq} (@command{gcc})
4825 The @code{q} stands for quit (really ``don't quit'').
4827 In normal operation mode, the compiler first parses the program and
4828 determines if there are any syntax errors. If there are, appropriate
4829 error messages are generated and compilation is immediately terminated.
4831 GNAT to continue with semantic analysis even if syntax errors have been
4832 found. This may enable the detection of more errors in a single run. On
4833 the other hand, the semantic analyzer is more likely to encounter some
4834 internal fatal error when given a syntactically invalid tree.
4837 @cindex @option{-gnatQ} (@command{gcc})
4838 In normal operation mode, the @file{ALI} file is not generated if any
4839 illegalities are detected in the program. The use of @option{-gnatQ} forces
4840 generation of the @file{ALI} file. This file is marked as being in
4841 error, so it cannot be used for binding purposes, but it does contain
4842 reasonably complete cross-reference information, and thus may be useful
4843 for use by tools (e.g., semantic browsing tools or integrated development
4844 environments) that are driven from the @file{ALI} file. This switch
4845 implies @option{-gnatq}, since the semantic phase must be run to get a
4846 meaningful ALI file.
4848 In addition, if @option{-gnatt} is also specified, then the tree file is
4849 generated even if there are illegalities. It may be useful in this case
4850 to also specify @option{-gnatq} to ensure that full semantic processing
4851 occurs. The resulting tree file can be processed by ASIS, for the purpose
4852 of providing partial information about illegal units, but if the error
4853 causes the tree to be badly malformed, then ASIS may crash during the
4856 When @option{-gnatQ} is used and the generated @file{ALI} file is marked as
4857 being in error, @command{gnatmake} will attempt to recompile the source when it
4858 finds such an @file{ALI} file, including with switch @option{-gnatc}.
4860 Note that @option{-gnatQ} has no effect if @option{-gnats} is specified,
4861 since ALI files are never generated if @option{-gnats} is set.
4865 @node Warning Message Control
4866 @subsection Warning Message Control
4867 @cindex Warning messages
4869 In addition to error messages, which correspond to illegalities as defined
4870 in the Ada Reference Manual, the compiler detects two kinds of warning
4873 First, the compiler considers some constructs suspicious and generates a
4874 warning message to alert you to a possible error. Second, if the
4875 compiler detects a situation that is sure to raise an exception at
4876 run time, it generates a warning message. The following shows an example
4877 of warning messages:
4879 e.adb:4:24: warning: creation of object may raise Storage_Error
4880 e.adb:10:17: warning: static value out of range
4881 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
4885 GNAT considers a large number of situations as appropriate
4886 for the generation of warning messages. As always, warnings are not
4887 definite indications of errors. For example, if you do an out-of-range
4888 assignment with the deliberate intention of raising a
4889 @code{Constraint_Error} exception, then the warning that may be
4890 issued does not indicate an error. Some of the situations for which GNAT
4891 issues warnings (at least some of the time) are given in the following
4892 list. This list is not complete, and new warnings are often added to
4893 subsequent versions of GNAT. The list is intended to give a general idea
4894 of the kinds of warnings that are generated.
4898 Possible infinitely recursive calls
4901 Out-of-range values being assigned
4904 Possible order of elaboration problems
4907 Assertions (pragma Assert) that are sure to fail
4913 Address clauses with possibly unaligned values, or where an attempt is
4914 made to overlay a smaller variable with a larger one.
4917 Fixed-point type declarations with a null range
4920 Direct_IO or Sequential_IO instantiated with a type that has access values
4923 Variables that are never assigned a value
4926 Variables that are referenced before being initialized
4929 Task entries with no corresponding @code{accept} statement
4932 Duplicate accepts for the same task entry in a @code{select}
4935 Objects that take too much storage
4938 Unchecked conversion between types of differing sizes
4941 Missing @code{return} statement along some execution path in a function
4944 Incorrect (unrecognized) pragmas
4947 Incorrect external names
4950 Allocation from empty storage pool
4953 Potentially blocking operation in protected type
4956 Suspicious parenthesization of expressions
4959 Mismatching bounds in an aggregate
4962 Attempt to return local value by reference
4965 Premature instantiation of a generic body
4968 Attempt to pack aliased components
4971 Out of bounds array subscripts
4974 Wrong length on string assignment
4977 Violations of style rules if style checking is enabled
4980 Unused @code{with} clauses
4983 @code{Bit_Order} usage that does not have any effect
4986 @code{Standard.Duration} used to resolve universal fixed expression
4989 Dereference of possibly null value
4992 Declaration that is likely to cause storage error
4995 Internal GNAT unit @code{with}'ed by application unit
4998 Values known to be out of range at compile time
5001 Unreferenced labels and variables
5004 Address overlays that could clobber memory
5007 Unexpected initialization when address clause present
5010 Bad alignment for address clause
5013 Useless type conversions
5016 Redundant assignment statements and other redundant constructs
5019 Useless exception handlers
5022 Accidental hiding of name by child unit
5025 Access before elaboration detected at compile time
5028 A range in a @code{for} loop that is known to be null or might be null
5033 The following section lists compiler switches that are available
5034 to control the handling of warning messages. It is also possible
5035 to exercise much finer control over what warnings are issued and
5036 suppressed using the GNAT pragma Warnings, @xref{Pragma Warnings,,,
5037 gnat_rm, GNAT Reference manual}.
5042 @emph{Activate all optional errors.}
5043 @cindex @option{-gnatwa} (@command{gcc})
5044 This switch activates most optional warning messages, see remaining list
5045 in this section for details on optional warning messages that can be
5046 individually controlled. The warnings that are not turned on by this
5048 @option{-gnatwd} (implicit dereferencing),
5049 @option{-gnatwh} (hiding),
5050 @option{-gnatwl} (elaboration warnings),
5051 @option{-gnatw.o} (warn on values set by out parameters ignored)
5052 and @option{-gnatwt} (tracking of deleted conditional code).
5053 All other optional warnings are turned on.
5056 @emph{Suppress all optional errors.}
5057 @cindex @option{-gnatwA} (@command{gcc})
5058 This switch suppresses all optional warning messages, see remaining list
5059 in this section for details on optional warning messages that can be
5060 individually controlled.
5063 @emph{Activate warnings on failing assertions.}
5064 @cindex @option{-gnatw.a} (@command{gcc})
5065 @cindex Assert failures
5066 This switch activates warnings for assertions where the compiler can tell at
5067 compile time that the assertion will fail. Note that this warning is given
5068 even if assertions are disabled. The default is that such warnings are
5072 @emph{Suppress warnings on failing assertions.}
5073 @cindex @option{-gnatw.A} (@command{gcc})
5074 @cindex Assert failures
5075 This switch suppresses warnings for assertions where the compiler can tell at
5076 compile time that the assertion will fail.
5079 @emph{Activate warnings on bad fixed values.}
5080 @cindex @option{-gnatwb} (@command{gcc})
5081 @cindex Bad fixed values
5082 @cindex Fixed-point Small value
5084 This switch activates warnings for static fixed-point expressions whose
5085 value is not an exact multiple of Small. Such values are implementation
5086 dependent, since an implementation is free to choose either of the multiples
5087 that surround the value. GNAT always chooses the closer one, but this is not
5088 required behavior, and it is better to specify a value that is an exact
5089 multiple, ensuring predictable execution. The default is that such warnings
5093 @emph{Suppress warnings on bad fixed values.}
5094 @cindex @option{-gnatwB} (@command{gcc})
5095 This switch suppresses warnings for static fixed-point expressions whose
5096 value is not an exact multiple of Small.
5099 @emph{Activate warnings on biased representation.}
5100 @cindex @option{-gnatw.b} (@command{gcc})
5101 @cindex Biased representation
5102 This switch activates warnings when a size clause, value size clause, component
5103 clause, or component size clause forces the use of biased representation for an
5104 integer type (e.g. representing a range of 10..11 in a single bit by using 0/1
5105 to represent 10/11). The default is that such warnings are generated.
5108 @emph{Suppress warnings on biased representation.}
5109 @cindex @option{-gnatwB} (@command{gcc})
5110 This switch suppresses warnings for representation clauses that force the use
5111 of biased representation.
5114 @emph{Activate warnings on conditionals.}
5115 @cindex @option{-gnatwc} (@command{gcc})
5116 @cindex Conditionals, constant
5117 This switch activates warnings for conditional expressions used in
5118 tests that are known to be True or False at compile time. The default
5119 is that such warnings are not generated.
5120 Note that this warning does
5121 not get issued for the use of boolean variables or constants whose
5122 values are known at compile time, since this is a standard technique
5123 for conditional compilation in Ada, and this would generate too many
5124 false positive warnings.
5126 This warning option also activates a special test for comparisons using
5127 the operators ``>='' and`` <=''.
5128 If the compiler can tell that only the equality condition is possible,
5129 then it will warn that the ``>'' or ``<'' part of the test
5130 is useless and that the operator could be replaced by ``=''.
5131 An example would be comparing a @code{Natural} variable <= 0.
5133 This warning option also generates warnings if
5134 one or both tests is optimized away in a membership test for integer
5135 values if the result can be determined at compile time. Range tests on
5136 enumeration types are not included, since it is common for such tests
5137 to include an end point.
5139 This warning can also be turned on using @option{-gnatwa}.
5142 @emph{Suppress warnings on conditionals.}
5143 @cindex @option{-gnatwC} (@command{gcc})
5144 This switch suppresses warnings for conditional expressions used in
5145 tests that are known to be True or False at compile time.
5148 @emph{Activate warnings on missing component clauses.}
5149 @cindex @option{-gnatw.c} (@command{gcc})
5150 @cindex Component clause, missing
5151 This switch activates warnings for record components where a record
5152 representation clause is present and has component clauses for the
5153 majority, but not all, of the components. A warning is given for each
5154 component for which no component clause is present.
5156 This warning can also be turned on using @option{-gnatwa}.
5159 @emph{Suppress warnings on missing component clauses.}
5160 @cindex @option{-gnatwC} (@command{gcc})
5161 This switch suppresses warnings for record components that are
5162 missing a component clause in the situation described above.
5165 @emph{Activate warnings on implicit dereferencing.}
5166 @cindex @option{-gnatwd} (@command{gcc})
5167 If this switch is set, then the use of a prefix of an access type
5168 in an indexed component, slice, or selected component without an
5169 explicit @code{.all} will generate a warning. With this warning
5170 enabled, access checks occur only at points where an explicit
5171 @code{.all} appears in the source code (assuming no warnings are
5172 generated as a result of this switch). The default is that such
5173 warnings are not generated.
5174 Note that @option{-gnatwa} does not affect the setting of
5175 this warning option.
5178 @emph{Suppress warnings on implicit dereferencing.}
5179 @cindex @option{-gnatwD} (@command{gcc})
5180 @cindex Implicit dereferencing
5181 @cindex Dereferencing, implicit
5182 This switch suppresses warnings for implicit dereferences in
5183 indexed components, slices, and selected components.
5186 @emph{Treat warnings as errors.}
5187 @cindex @option{-gnatwe} (@command{gcc})
5188 @cindex Warnings, treat as error
5189 This switch causes warning messages to be treated as errors.
5190 The warning string still appears, but the warning messages are counted
5191 as errors, and prevent the generation of an object file.
5194 @emph{Activate every optional warning}
5195 @cindex @option{-gnatw.e} (@command{gcc})
5196 @cindex Warnings, activate every optional warning
5197 This switch activates all optional warnings, including those which
5198 are not activated by @code{-gnatwa}.
5201 @emph{Activate warnings on unreferenced formals.}
5202 @cindex @option{-gnatwf} (@command{gcc})
5203 @cindex Formals, unreferenced
5204 This switch causes a warning to be generated if a formal parameter
5205 is not referenced in the body of the subprogram. This warning can
5206 also be turned on using @option{-gnatwa} or @option{-gnatwu}. The
5207 default is that these warnings are not generated.
5210 @emph{Suppress warnings on unreferenced formals.}
5211 @cindex @option{-gnatwF} (@command{gcc})
5212 This switch suppresses warnings for unreferenced formal
5213 parameters. Note that the
5214 combination @option{-gnatwu} followed by @option{-gnatwF} has the
5215 effect of warning on unreferenced entities other than subprogram
5219 @emph{Activate warnings on unrecognized pragmas.}
5220 @cindex @option{-gnatwg} (@command{gcc})
5221 @cindex Pragmas, unrecognized
5222 This switch causes a warning to be generated if an unrecognized
5223 pragma is encountered. Apart from issuing this warning, the
5224 pragma is ignored and has no effect. This warning can
5225 also be turned on using @option{-gnatwa}. The default
5226 is that such warnings are issued (satisfying the Ada Reference
5227 Manual requirement that such warnings appear).
5230 @emph{Suppress warnings on unrecognized pragmas.}
5231 @cindex @option{-gnatwG} (@command{gcc})
5232 This switch suppresses warnings for unrecognized pragmas.
5235 @emph{Activate warnings on hiding.}
5236 @cindex @option{-gnatwh} (@command{gcc})
5237 @cindex Hiding of Declarations
5238 This switch activates warnings on hiding declarations.
5239 A declaration is considered hiding
5240 if it is for a non-overloadable entity, and it declares an entity with the
5241 same name as some other entity that is directly or use-visible. The default
5242 is that such warnings are not generated.
5243 Note that @option{-gnatwa} does not affect the setting of this warning option.
5246 @emph{Suppress warnings on hiding.}
5247 @cindex @option{-gnatwH} (@command{gcc})
5248 This switch suppresses warnings on hiding declarations.
5251 @emph{Activate warnings on implementation units.}
5252 @cindex @option{-gnatwi} (@command{gcc})
5253 This switch activates warnings for a @code{with} of an internal GNAT
5254 implementation unit, defined as any unit from the @code{Ada},
5255 @code{Interfaces}, @code{GNAT},
5256 ^^@code{DEC},^ or @code{System}
5257 hierarchies that is not
5258 documented in either the Ada Reference Manual or the GNAT
5259 Programmer's Reference Manual. Such units are intended only
5260 for internal implementation purposes and should not be @code{with}'ed
5261 by user programs. The default is that such warnings are generated
5262 This warning can also be turned on using @option{-gnatwa}.
5265 @emph{Disable warnings on implementation units.}
5266 @cindex @option{-gnatwI} (@command{gcc})
5267 This switch disables warnings for a @code{with} of an internal GNAT
5268 implementation unit.
5271 @emph{Activate warnings on obsolescent features (Annex J).}
5272 @cindex @option{-gnatwj} (@command{gcc})
5273 @cindex Features, obsolescent
5274 @cindex Obsolescent features
5275 If this warning option is activated, then warnings are generated for
5276 calls to subprograms marked with @code{pragma Obsolescent} and
5277 for use of features in Annex J of the Ada Reference Manual. In the
5278 case of Annex J, not all features are flagged. In particular use
5279 of the renamed packages (like @code{Text_IO}) and use of package
5280 @code{ASCII} are not flagged, since these are very common and
5281 would generate many annoying positive warnings. The default is that
5282 such warnings are not generated. This warning is also turned on by
5283 the use of @option{-gnatwa}.
5285 In addition to the above cases, warnings are also generated for
5286 GNAT features that have been provided in past versions but which
5287 have been superseded (typically by features in the new Ada standard).
5288 For example, @code{pragma Ravenscar} will be flagged since its
5289 function is replaced by @code{pragma Profile(Ravenscar)}.
5291 Note that this warning option functions differently from the
5292 restriction @code{No_Obsolescent_Features} in two respects.
5293 First, the restriction applies only to annex J features.
5294 Second, the restriction does flag uses of package @code{ASCII}.
5297 @emph{Suppress warnings on obsolescent features (Annex J).}
5298 @cindex @option{-gnatwJ} (@command{gcc})
5299 This switch disables warnings on use of obsolescent features.
5302 @emph{Activate warnings on variables that could be constants.}
5303 @cindex @option{-gnatwk} (@command{gcc})
5304 This switch activates warnings for variables that are initialized but
5305 never modified, and then could be declared constants. The default is that
5306 such warnings are not given.
5307 This warning can also be turned on using @option{-gnatwa}.
5310 @emph{Suppress warnings on variables that could be constants.}
5311 @cindex @option{-gnatwK} (@command{gcc})
5312 This switch disables warnings on variables that could be declared constants.
5315 @emph{Activate warnings for elaboration pragmas.}
5316 @cindex @option{-gnatwl} (@command{gcc})
5317 @cindex Elaboration, warnings
5318 This switch activates warnings on missing
5319 @code{Elaborate_All} and @code{Elaborate} pragmas.
5320 See the section in this guide on elaboration checking for details on
5321 when such pragmas should be used. In dynamic elaboration mode, this switch
5322 generations warnings about the need to add elaboration pragmas. Note however,
5323 that if you blindly follow these warnings, and add @code{Elaborate_All}
5324 warnings wherever they are recommended, you basically end up with the
5325 equivalent of the static elaboration model, which may not be what you want for
5326 legacy code for which the static model does not work.
5328 For the static model, the messages generated are labeled "info:" (for
5329 information messages). They are not warnings to add elaboration pragmas,
5330 merely informational messages showing what implicit elaboration pragmas
5331 have been added, for use in analyzing elaboration circularity problems.
5333 Warnings are also generated if you
5334 are using the static mode of elaboration, and a @code{pragma Elaborate}
5335 is encountered. The default is that such warnings
5337 This warning is not automatically turned on by the use of @option{-gnatwa}.
5340 @emph{Suppress warnings for elaboration pragmas.}
5341 @cindex @option{-gnatwL} (@command{gcc})
5342 This switch suppresses warnings on missing Elaborate and Elaborate_All pragmas.
5343 See the section in this guide on elaboration checking for details on
5344 when such pragmas should be used.
5347 @emph{Activate warnings on modified but unreferenced variables.}
5348 @cindex @option{-gnatwm} (@command{gcc})
5349 This switch activates warnings for variables that are assigned (using
5350 an initialization value or with one or more assignment statements) but
5351 whose value is never read. The warning is suppressed for volatile
5352 variables and also for variables that are renamings of other variables
5353 or for which an address clause is given.
5354 This warning can also be turned on using @option{-gnatwa}.
5355 The default is that these warnings are not given.
5358 @emph{Disable warnings on modified but unreferenced variables.}
5359 @cindex @option{-gnatwM} (@command{gcc})
5360 This switch disables warnings for variables that are assigned or
5361 initialized, but never read.
5364 @emph{Activate warnings on suspicious modulus values.}
5365 @cindex @option{-gnatw.m} (@command{gcc})
5366 This switch activates warnings for modulus values that seem suspicious.
5367 The cases caught are where the size is the same as the modulus (e.g.
5368 a modulus of 7 with a size of 7 bits), and modulus values of 32 or 64
5369 with no size clause. The guess in both cases is that 2**x was intended
5370 rather than x. The default is that these warnings are given.
5373 @emph{Disable warnings on suspicious modulus values.}
5374 @cindex @option{-gnatw.M} (@command{gcc})
5375 This switch disables warnings for suspicious modulus values.
5378 @emph{Set normal warnings mode.}
5379 @cindex @option{-gnatwn} (@command{gcc})
5380 This switch sets normal warning mode, in which enabled warnings are
5381 issued and treated as warnings rather than errors. This is the default
5382 mode. the switch @option{-gnatwn} can be used to cancel the effect of
5383 an explicit @option{-gnatws} or
5384 @option{-gnatwe}. It also cancels the effect of the
5385 implicit @option{-gnatwe} that is activated by the
5386 use of @option{-gnatg}.
5389 @emph{Activate warnings on address clause overlays.}
5390 @cindex @option{-gnatwo} (@command{gcc})
5391 @cindex Address Clauses, warnings
5392 This switch activates warnings for possibly unintended initialization
5393 effects of defining address clauses that cause one variable to overlap
5394 another. The default is that such warnings are generated.
5395 This warning can also be turned on using @option{-gnatwa}.
5398 @emph{Suppress warnings on address clause overlays.}
5399 @cindex @option{-gnatwO} (@command{gcc})
5400 This switch suppresses warnings on possibly unintended initialization
5401 effects of defining address clauses that cause one variable to overlap
5405 @emph{Activate warnings on modified but unreferenced out parameters.}
5406 @cindex @option{-gnatw.o} (@command{gcc})
5407 This switch activates warnings for variables that are modified by using
5408 them as actuals for a call to a procedure with an out mode formal, where
5409 the resulting assigned value is never read. It is applicable in the case
5410 where there is more than one out mode formal. If there is only one out
5411 mode formal, the warning is issued by default (controlled by -gnatwu).
5412 The warning is suppressed for volatile
5413 variables and also for variables that are renamings of other variables
5414 or for which an address clause is given.
5415 The default is that these warnings are not given. Note that this warning
5416 is not included in -gnatwa, it must be activated explicitly.
5419 @emph{Disable warnings on modified but unreferenced out parameters.}
5420 @cindex @option{-gnatw.O} (@command{gcc})
5421 This switch suppresses warnings for variables that are modified by using
5422 them as actuals for a call to a procedure with an out mode formal, where
5423 the resulting assigned value is never read.
5426 @emph{Activate warnings on ineffective pragma Inlines.}
5427 @cindex @option{-gnatwp} (@command{gcc})
5428 @cindex Inlining, warnings
5429 This switch activates warnings for failure of front end inlining
5430 (activated by @option{-gnatN}) to inline a particular call. There are
5431 many reasons for not being able to inline a call, including most
5432 commonly that the call is too complex to inline. The default is
5433 that such warnings are not given.
5434 This warning can also be turned on using @option{-gnatwa}.
5435 Warnings on ineffective inlining by the gcc back-end can be activated
5436 separately, using the gcc switch -Winline.
5439 @emph{Suppress warnings on ineffective pragma Inlines.}
5440 @cindex @option{-gnatwP} (@command{gcc})
5441 This switch suppresses warnings on ineffective pragma Inlines. If the
5442 inlining mechanism cannot inline a call, it will simply ignore the
5446 @emph{Activate warnings on parameter ordering.}
5447 @cindex @option{-gnatw.p} (@command{gcc})
5448 @cindex Parameter order, warnings
5449 This switch activates warnings for cases of suspicious parameter
5450 ordering when the list of arguments are all simple identifiers that
5451 match the names of the formals, but are in a different order. The
5452 warning is suppressed if any use of named parameter notation is used,
5453 so this is the appropriate way to suppress a false positive (and
5454 serves to emphasize that the "misordering" is deliberate). The
5456 that such warnings are not given.
5457 This warning can also be turned on using @option{-gnatwa}.
5460 @emph{Suppress warnings on parameter ordering.}
5461 @cindex @option{-gnatw.P} (@command{gcc})
5462 This switch suppresses warnings on cases of suspicious parameter
5466 @emph{Activate warnings on questionable missing parentheses.}
5467 @cindex @option{-gnatwq} (@command{gcc})
5468 @cindex Parentheses, warnings
5469 This switch activates warnings for cases where parentheses are not used and
5470 the result is potential ambiguity from a readers point of view. For example
5471 (not a > b) when a and b are modular means ((not a) > b) and very likely the
5472 programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and
5473 quite likely ((-x) mod 5) was intended. In such situations it seems best to
5474 follow the rule of always parenthesizing to make the association clear, and
5475 this warning switch warns if such parentheses are not present. The default
5476 is that these warnings are given.
5477 This warning can also be turned on using @option{-gnatwa}.
5480 @emph{Suppress warnings on questionable missing parentheses.}
5481 @cindex @option{-gnatwQ} (@command{gcc})
5482 This switch suppresses warnings for cases where the association is not
5483 clear and the use of parentheses is preferred.
5486 @emph{Activate warnings on redundant constructs.}
5487 @cindex @option{-gnatwr} (@command{gcc})
5488 This switch activates warnings for redundant constructs. The following
5489 is the current list of constructs regarded as redundant:
5493 Assignment of an item to itself.
5495 Type conversion that converts an expression to its own type.
5497 Use of the attribute @code{Base} where @code{typ'Base} is the same
5500 Use of pragma @code{Pack} when all components are placed by a record
5501 representation clause.
5503 Exception handler containing only a reraise statement (raise with no
5504 operand) which has no effect.
5506 Use of the operator abs on an operand that is known at compile time
5509 Comparison of boolean expressions to an explicit True value.
5512 This warning can also be turned on using @option{-gnatwa}.
5513 The default is that warnings for redundant constructs are not given.
5516 @emph{Suppress warnings on redundant constructs.}
5517 @cindex @option{-gnatwR} (@command{gcc})
5518 This switch suppresses warnings for redundant constructs.
5521 @emph{Activate warnings for object renaming function.}
5522 @cindex @option{-gnatw.r} (@command{gcc})
5523 This switch activates warnings for an object renaming that renames a
5524 function call, which is equivalent to a constant declaration (as
5525 opposed to renaming the function itself). The default is that these
5526 warnings are given. This warning can also be turned on using
5530 @emph{Suppress warnings for object renaming function.}
5531 @cindex @option{-gnatwT} (@command{gcc})
5532 This switch suppresses warnings for object renaming function.
5535 @emph{Suppress all warnings.}
5536 @cindex @option{-gnatws} (@command{gcc})
5537 This switch completely suppresses the
5538 output of all warning messages from the GNAT front end.
5539 Note that it does not suppress warnings from the @command{gcc} back end.
5540 To suppress these back end warnings as well, use the switch @option{-w}
5541 in addition to @option{-gnatws}.
5544 @emph{Activate warnings for tracking of deleted conditional code.}
5545 @cindex @option{-gnatwt} (@command{gcc})
5546 @cindex Deactivated code, warnings
5547 @cindex Deleted code, warnings
5548 This switch activates warnings for tracking of code in conditionals (IF and
5549 CASE statements) that is detected to be dead code which cannot be executed, and
5550 which is removed by the front end. This warning is off by default, and is not
5551 turned on by @option{-gnatwa}, it has to be turned on explicitly. This may be
5552 useful for detecting deactivated code in certified applications.
5555 @emph{Suppress warnings for tracking of deleted conditional code.}
5556 @cindex @option{-gnatwT} (@command{gcc})
5557 This switch suppresses warnings for tracking of deleted conditional code.
5560 @emph{Activate warnings on unused entities.}
5561 @cindex @option{-gnatwu} (@command{gcc})
5562 This switch activates warnings to be generated for entities that
5563 are declared but not referenced, and for units that are @code{with}'ed
5565 referenced. In the case of packages, a warning is also generated if
5566 no entities in the package are referenced. This means that if the package
5567 is referenced but the only references are in @code{use}
5568 clauses or @code{renames}
5569 declarations, a warning is still generated. A warning is also generated
5570 for a generic package that is @code{with}'ed but never instantiated.
5571 In the case where a package or subprogram body is compiled, and there
5572 is a @code{with} on the corresponding spec
5573 that is only referenced in the body,
5574 a warning is also generated, noting that the
5575 @code{with} can be moved to the body. The default is that
5576 such warnings are not generated.
5577 This switch also activates warnings on unreferenced formals
5578 (it includes the effect of @option{-gnatwf}).
5579 This warning can also be turned on using @option{-gnatwa}.
5582 @emph{Suppress warnings on unused entities.}
5583 @cindex @option{-gnatwU} (@command{gcc})
5584 This switch suppresses warnings for unused entities and packages.
5585 It also turns off warnings on unreferenced formals (and thus includes
5586 the effect of @option{-gnatwF}).
5589 @emph{Activate warnings on unassigned variables.}
5590 @cindex @option{-gnatwv} (@command{gcc})
5591 @cindex Unassigned variable warnings
5592 This switch activates warnings for access to variables which
5593 may not be properly initialized. The default is that
5594 such warnings are generated.
5595 This warning can also be turned on using @option{-gnatwa}.
5598 @emph{Suppress warnings on unassigned variables.}
5599 @cindex @option{-gnatwV} (@command{gcc})
5600 This switch suppresses warnings for access to variables which
5601 may not be properly initialized.
5602 For variables of a composite type, the warning can also be suppressed in
5603 Ada 2005 by using a default initialization with a box. For example, if
5604 Table is an array of records whose components are only partially uninitialized,
5605 then the following code:
5607 @smallexample @c ada
5608 Tab : Table := (others => <>);
5611 will suppress warnings on subsequent statements that access components
5615 @emph{Activate warnings on wrong low bound assumption.}
5616 @cindex @option{-gnatww} (@command{gcc})
5617 @cindex String indexing warnings
5618 This switch activates warnings for indexing an unconstrained string parameter
5619 with a literal or S'Length. This is a case where the code is assuming that the
5620 low bound is one, which is in general not true (for example when a slice is
5621 passed). The default is that such warnings are generated.
5622 This warning can also be turned on using @option{-gnatwa}.
5625 @emph{Suppress warnings on wrong low bound assumption.}
5626 @cindex @option{-gnatwW} (@command{gcc})
5627 This switch suppresses warnings for indexing an unconstrained string parameter
5628 with a literal or S'Length. Note that this warning can also be suppressed
5629 in a particular case by adding an
5630 assertion that the lower bound is 1,
5631 as shown in the following example.
5633 @smallexample @c ada
5634 procedure K (S : String) is
5635 pragma Assert (S'First = 1);
5640 @emph{Activate warnings on unnecessary Warnings Off pragmas}
5641 @cindex @option{-gnatw.w} (@command{gcc})
5642 @cindex Warnings Off control
5643 This switch activates warnings for use of @code{pragma Warnings (Off, entity}
5644 where either the pragma is entirely useless (because it suppresses no
5645 warnings), or it could be replaced by @code{pragma Unreferenced} or
5646 @code{pragma Unmodified}.The default is that these warnings are not given.
5647 Note that this warning is not included in -gnatwa, it must be
5648 activated explicitly.
5651 @emph{Suppress warnings on unnecessary Warnings Off pragmas}
5652 @cindex @option{-gnatw.W} (@command{gcc})
5653 This switch suppresses warnings for use of @code{pragma Warnings (Off, entity}.
5656 @emph{Activate warnings on Export/Import pragmas.}
5657 @cindex @option{-gnatwx} (@command{gcc})
5658 @cindex Export/Import pragma warnings
5659 This switch activates warnings on Export/Import pragmas when
5660 the compiler detects a possible conflict between the Ada and
5661 foreign language calling sequences. For example, the use of
5662 default parameters in a convention C procedure is dubious
5663 because the C compiler cannot supply the proper default, so
5664 a warning is issued. The default is that such warnings are
5666 This warning can also be turned on using @option{-gnatwa}.
5669 @emph{Suppress warnings on Export/Import pragmas.}
5670 @cindex @option{-gnatwX} (@command{gcc})
5671 This switch suppresses warnings on Export/Import pragmas.
5672 The sense of this is that you are telling the compiler that
5673 you know what you are doing in writing the pragma, and it
5674 should not complain at you.
5677 @emph{Activate warnings for No_Exception_Propagation mode.}
5678 @cindex @option{-gnatwm} (@command{gcc})
5679 This switch activates warnings for exception usage when pragma Restrictions
5680 (No_Exception_Propagation) is in effect. Warnings are given for implicit or
5681 explicit exception raises which are not covered by a local handler, and for
5682 exception handlers which do not cover a local raise. The default is that these
5683 warnings are not given.
5686 @emph{Disable warnings for No_Exception_Propagation mode.}
5687 This switch disables warnings for exception usage when pragma Restrictions
5688 (No_Exception_Propagation) is in effect.
5691 @emph{Activate warnings for Ada 2005 compatibility issues.}
5692 @cindex @option{-gnatwy} (@command{gcc})
5693 @cindex Ada 2005 compatibility issues warnings
5694 For the most part Ada 2005 is upwards compatible with Ada 95,
5695 but there are some exceptions (for example the fact that
5696 @code{interface} is now a reserved word in Ada 2005). This
5697 switch activates several warnings to help in identifying
5698 and correcting such incompatibilities. The default is that
5699 these warnings are generated. Note that at one point Ada 2005
5700 was called Ada 0Y, hence the choice of character.
5701 This warning can also be turned on using @option{-gnatwa}.
5704 @emph{Disable warnings for Ada 2005 compatibility issues.}
5705 @cindex @option{-gnatwY} (@command{gcc})
5706 @cindex Ada 2005 compatibility issues warnings
5707 This switch suppresses several warnings intended to help in identifying
5708 incompatibilities between Ada 95 and Ada 2005.
5711 @emph{Activate warnings on unchecked conversions.}
5712 @cindex @option{-gnatwz} (@command{gcc})
5713 @cindex Unchecked_Conversion warnings
5714 This switch activates warnings for unchecked conversions
5715 where the types are known at compile time to have different
5717 is that such warnings are generated. Warnings are also
5718 generated for subprogram pointers with different conventions,
5719 and, on VMS only, for data pointers with different conventions.
5720 This warning can also be turned on using @option{-gnatwa}.
5723 @emph{Suppress warnings on unchecked conversions.}
5724 @cindex @option{-gnatwZ} (@command{gcc})
5725 This switch suppresses warnings for unchecked conversions
5726 where the types are known at compile time to have different
5727 sizes or conventions.
5729 @item ^-Wunused^WARNINGS=UNUSED^
5730 @cindex @option{-Wunused}
5731 The warnings controlled by the @option{-gnatw} switch are generated by
5732 the front end of the compiler. The @option{GCC} back end can provide
5733 additional warnings and they are controlled by the @option{-W} switch.
5734 For example, @option{^-Wunused^WARNINGS=UNUSED^} activates back end
5735 warnings for entities that are declared but not referenced.
5737 @item ^-Wuninitialized^WARNINGS=UNINITIALIZED^
5738 @cindex @option{-Wuninitialized}
5739 Similarly, @option{^-Wuninitialized^WARNINGS=UNINITIALIZED^} activates
5740 the back end warning for uninitialized variables. This switch must be
5741 used in conjunction with an optimization level greater than zero.
5743 @item ^-Wall^/ALL_BACK_END_WARNINGS^
5744 @cindex @option{-Wall}
5745 This switch enables all the above warnings from the @option{GCC} back end.
5746 The code generator detects a number of warning situations that are missed
5747 by the @option{GNAT} front end, and this switch can be used to activate them.
5748 The use of this switch also sets the default front end warning mode to
5749 @option{-gnatwa}, that is, most front end warnings activated as well.
5751 @item ^-w^/NO_BACK_END_WARNINGS^
5753 Conversely, this switch suppresses warnings from the @option{GCC} back end.
5754 The use of this switch also sets the default front end warning mode to
5755 @option{-gnatws}, that is, front end warnings suppressed as well.
5761 A string of warning parameters can be used in the same parameter. For example:
5768 will turn on all optional warnings except for elaboration pragma warnings,
5769 and also specify that warnings should be treated as errors.
5771 When no switch @option{^-gnatw^/WARNINGS^} is used, this is equivalent to:
5796 @node Debugging and Assertion Control
5797 @subsection Debugging and Assertion Control
5801 @cindex @option{-gnata} (@command{gcc})
5807 The pragmas @code{Assert} and @code{Debug} normally have no effect and
5808 are ignored. This switch, where @samp{a} stands for assert, causes
5809 @code{Assert} and @code{Debug} pragmas to be activated.
5811 The pragmas have the form:
5815 @b{pragma} Assert (@var{Boolean-expression} @r{[},
5816 @var{static-string-expression}@r{]})
5817 @b{pragma} Debug (@var{procedure call})
5822 The @code{Assert} pragma causes @var{Boolean-expression} to be tested.
5823 If the result is @code{True}, the pragma has no effect (other than
5824 possible side effects from evaluating the expression). If the result is
5825 @code{False}, the exception @code{Assert_Failure} declared in the package
5826 @code{System.Assertions} is
5827 raised (passing @var{static-string-expression}, if present, as the
5828 message associated with the exception). If no string expression is
5829 given the default is a string giving the file name and line number
5832 The @code{Debug} pragma causes @var{procedure} to be called. Note that
5833 @code{pragma Debug} may appear within a declaration sequence, allowing
5834 debugging procedures to be called between declarations.
5837 @item /DEBUG@r{[}=debug-level@r{]}
5839 Specifies how much debugging information is to be included in
5840 the resulting object file where 'debug-level' is one of the following:
5843 Include both debugger symbol records and traceback
5845 This is the default setting.
5847 Include both debugger symbol records and traceback in
5850 Excludes both debugger symbol records and traceback
5851 the object file. Same as /NODEBUG.
5853 Includes only debugger symbol records in the object
5854 file. Note that this doesn't include traceback information.
5859 @node Validity Checking
5860 @subsection Validity Checking
5861 @findex Validity Checking
5864 The Ada Reference Manual defines the concept of invalid values (see
5865 RM 13.9.1). The primary source of invalid values is uninitialized
5866 variables. A scalar variable that is left uninitialized may contain
5867 an invalid value; the concept of invalid does not apply to access or
5870 It is an error to read an invalid value, but the RM does not require
5871 run-time checks to detect such errors, except for some minimal
5872 checking to prevent erroneous execution (i.e. unpredictable
5873 behavior). This corresponds to the @option{-gnatVd} switch below,
5874 which is the default. For example, by default, if the expression of a
5875 case statement is invalid, it will raise Constraint_Error rather than
5876 causing a wild jump, and if an array index on the left-hand side of an
5877 assignment is invalid, it will raise Constraint_Error rather than
5878 overwriting an arbitrary memory location.
5880 The @option{-gnatVa} may be used to enable additional validity checks,
5881 which are not required by the RM. These checks are often very
5882 expensive (which is why the RM does not require them). These checks
5883 are useful in tracking down uninitialized variables, but they are
5884 not usually recommended for production builds.
5886 The other @option{-gnatV^@var{x}^^} switches below allow finer-grained
5887 control; you can enable whichever validity checks you desire. However,
5888 for most debugging purposes, @option{-gnatVa} is sufficient, and the
5889 default @option{-gnatVd} (i.e. standard Ada behavior) is usually
5890 sufficient for non-debugging use.
5892 The @option{-gnatB} switch tells the compiler to assume that all
5893 values are valid (that is, within their declared subtype range)
5894 except in the context of a use of the Valid attribute. This means
5895 the compiler can generate more efficient code, since the range
5896 of values is better known at compile time. However, an uninitialized
5897 variable can cause wild jumps and memory corruption in this mode.
5899 The @option{-gnatV^@var{x}^^} switch allows control over the validity
5900 checking mode as described below.
5902 The @code{x} argument is a string of letters that
5903 indicate validity checks that are performed or not performed in addition
5904 to the default checks required by Ada as described above.
5907 The options allowed for this qualifier
5908 indicate validity checks that are performed or not performed in addition
5909 to the default checks required by Ada as described above.
5915 @emph{All validity checks.}
5916 @cindex @option{-gnatVa} (@command{gcc})
5917 All validity checks are turned on.
5919 That is, @option{-gnatVa} is
5920 equivalent to @option{gnatVcdfimorst}.
5924 @emph{Validity checks for copies.}
5925 @cindex @option{-gnatVc} (@command{gcc})
5926 The right hand side of assignments, and the initializing values of
5927 object declarations are validity checked.
5930 @emph{Default (RM) validity checks.}
5931 @cindex @option{-gnatVd} (@command{gcc})
5932 Some validity checks are done by default following normal Ada semantics
5934 A check is done in case statements that the expression is within the range
5935 of the subtype. If it is not, Constraint_Error is raised.
5936 For assignments to array components, a check is done that the expression used
5937 as index is within the range. If it is not, Constraint_Error is raised.
5938 Both these validity checks may be turned off using switch @option{-gnatVD}.
5939 They are turned on by default. If @option{-gnatVD} is specified, a subsequent
5940 switch @option{-gnatVd} will leave the checks turned on.
5941 Switch @option{-gnatVD} should be used only if you are sure that all such
5942 expressions have valid values. If you use this switch and invalid values
5943 are present, then the program is erroneous, and wild jumps or memory
5944 overwriting may occur.
5947 @emph{Validity checks for elementary components.}
5948 @cindex @option{-gnatVe} (@command{gcc})
5949 In the absence of this switch, assignments to record or array components are
5950 not validity checked, even if validity checks for assignments generally
5951 (@option{-gnatVc}) are turned on. In Ada, assignment of composite values do not
5952 require valid data, but assignment of individual components does. So for
5953 example, there is a difference between copying the elements of an array with a
5954 slice assignment, compared to assigning element by element in a loop. This
5955 switch allows you to turn off validity checking for components, even when they
5956 are assigned component by component.
5959 @emph{Validity checks for floating-point values.}
5960 @cindex @option{-gnatVf} (@command{gcc})
5961 In the absence of this switch, validity checking occurs only for discrete
5962 values. If @option{-gnatVf} is specified, then validity checking also applies
5963 for floating-point values, and NaNs and infinities are considered invalid,
5964 as well as out of range values for constrained types. Note that this means
5965 that standard IEEE infinity mode is not allowed. The exact contexts
5966 in which floating-point values are checked depends on the setting of other
5967 options. For example,
5968 @option{^-gnatVif^VALIDITY_CHECKING=(IN_PARAMS,FLOATS)^} or
5969 @option{^-gnatVfi^VALIDITY_CHECKING=(FLOATS,IN_PARAMS)^}
5970 (the order does not matter) specifies that floating-point parameters of mode
5971 @code{in} should be validity checked.
5974 @emph{Validity checks for @code{in} mode parameters}
5975 @cindex @option{-gnatVi} (@command{gcc})
5976 Arguments for parameters of mode @code{in} are validity checked in function
5977 and procedure calls at the point of call.
5980 @emph{Validity checks for @code{in out} mode parameters.}
5981 @cindex @option{-gnatVm} (@command{gcc})
5982 Arguments for parameters of mode @code{in out} are validity checked in
5983 procedure calls at the point of call. The @code{'m'} here stands for
5984 modify, since this concerns parameters that can be modified by the call.
5985 Note that there is no specific option to test @code{out} parameters,
5986 but any reference within the subprogram will be tested in the usual
5987 manner, and if an invalid value is copied back, any reference to it
5988 will be subject to validity checking.
5991 @emph{No validity checks.}
5992 @cindex @option{-gnatVn} (@command{gcc})
5993 This switch turns off all validity checking, including the default checking
5994 for case statements and left hand side subscripts. Note that the use of
5995 the switch @option{-gnatp} suppresses all run-time checks, including
5996 validity checks, and thus implies @option{-gnatVn}. When this switch
5997 is used, it cancels any other @option{-gnatV} previously issued.
6000 @emph{Validity checks for operator and attribute operands.}
6001 @cindex @option{-gnatVo} (@command{gcc})
6002 Arguments for predefined operators and attributes are validity checked.
6003 This includes all operators in package @code{Standard},
6004 the shift operators defined as intrinsic in package @code{Interfaces}
6005 and operands for attributes such as @code{Pos}. Checks are also made
6006 on individual component values for composite comparisons, and on the
6007 expressions in type conversions and qualified expressions. Checks are
6008 also made on explicit ranges using @samp{..} (e.g.@: slices, loops etc).
6011 @emph{Validity checks for parameters.}
6012 @cindex @option{-gnatVp} (@command{gcc})
6013 This controls the treatment of parameters within a subprogram (as opposed
6014 to @option{-gnatVi} and @option{-gnatVm} which control validity testing
6015 of parameters on a call. If either of these call options is used, then
6016 normally an assumption is made within a subprogram that the input arguments
6017 have been validity checking at the point of call, and do not need checking
6018 again within a subprogram). If @option{-gnatVp} is set, then this assumption
6019 is not made, and parameters are not assumed to be valid, so their validity
6020 will be checked (or rechecked) within the subprogram.
6023 @emph{Validity checks for function returns.}
6024 @cindex @option{-gnatVr} (@command{gcc})
6025 The expression in @code{return} statements in functions is validity
6029 @emph{Validity checks for subscripts.}
6030 @cindex @option{-gnatVs} (@command{gcc})
6031 All subscripts expressions are checked for validity, whether they appear
6032 on the right side or left side (in default mode only left side subscripts
6033 are validity checked).
6036 @emph{Validity checks for tests.}
6037 @cindex @option{-gnatVt} (@command{gcc})
6038 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
6039 statements are checked, as well as guard expressions in entry calls.
6044 The @option{-gnatV} switch may be followed by
6045 ^a string of letters^a list of options^
6046 to turn on a series of validity checking options.
6048 @option{^-gnatVcr^/VALIDITY_CHECKING=(COPIES, RETURNS)^}
6049 specifies that in addition to the default validity checking, copies and
6050 function return expressions are to be validity checked.
6051 In order to make it easier
6052 to specify the desired combination of effects,
6054 the upper case letters @code{CDFIMORST} may
6055 be used to turn off the corresponding lower case option.
6058 the prefix @code{NO} on an option turns off the corresponding validity
6061 @item @code{NOCOPIES}
6062 @item @code{NODEFAULT}
6063 @item @code{NOFLOATS}
6064 @item @code{NOIN_PARAMS}
6065 @item @code{NOMOD_PARAMS}
6066 @item @code{NOOPERANDS}
6067 @item @code{NORETURNS}
6068 @item @code{NOSUBSCRIPTS}
6069 @item @code{NOTESTS}
6073 @option{^-gnatVaM^/VALIDITY_CHECKING=(ALL, NOMOD_PARAMS)^}
6074 turns on all validity checking options except for
6075 checking of @code{@b{in out}} procedure arguments.
6077 The specification of additional validity checking generates extra code (and
6078 in the case of @option{-gnatVa} the code expansion can be substantial).
6079 However, these additional checks can be very useful in detecting
6080 uninitialized variables, incorrect use of unchecked conversion, and other
6081 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
6082 is useful in conjunction with the extra validity checking, since this
6083 ensures that wherever possible uninitialized variables have invalid values.
6085 See also the pragma @code{Validity_Checks} which allows modification of
6086 the validity checking mode at the program source level, and also allows for
6087 temporary disabling of validity checks.
6089 @node Style Checking
6090 @subsection Style Checking
6091 @findex Style checking
6094 The @option{-gnaty^x^(option,option,@dots{})^} switch
6095 @cindex @option{-gnaty} (@command{gcc})
6096 causes the compiler to
6097 enforce specified style rules. A limited set of style rules has been used
6098 in writing the GNAT sources themselves. This switch allows user programs
6099 to activate all or some of these checks. If the source program fails a
6100 specified style check, an appropriate warning message is given, preceded by
6101 the character sequence ``(style)''.
6103 @code{(option,option,@dots{})} is a sequence of keywords
6106 The string @var{x} is a sequence of letters or digits
6108 indicating the particular style
6109 checks to be performed. The following checks are defined:
6114 @emph{Specify indentation level.}
6115 If a digit from 1-9 appears
6116 ^in the string after @option{-gnaty}^as an option for /STYLE_CHECKS^
6117 then proper indentation is checked, with the digit indicating the
6118 indentation level required. A value of zero turns off this style check.
6119 The general style of required indentation is as specified by
6120 the examples in the Ada Reference Manual. Full line comments must be
6121 aligned with the @code{--} starting on a column that is a multiple of
6122 the alignment level, or they may be aligned the same way as the following
6123 non-blank line (this is useful when full line comments appear in the middle
6127 @emph{Check attribute casing.}
6128 Attribute names, including the case of keywords such as @code{digits}
6129 used as attributes names, must be written in mixed case, that is, the
6130 initial letter and any letter following an underscore must be uppercase.
6131 All other letters must be lowercase.
6133 @item ^A^ARRAY_INDEXES^
6134 @emph{Use of array index numbers in array attributes.}
6135 When using the array attributes First, Last, Range,
6136 or Length, the index number must be omitted for one-dimensional arrays
6137 and is required for multi-dimensional arrays.
6140 @emph{Blanks not allowed at statement end.}
6141 Trailing blanks are not allowed at the end of statements. The purpose of this
6142 rule, together with h (no horizontal tabs), is to enforce a canonical format
6143 for the use of blanks to separate source tokens.
6145 @item ^B^BOOLEAN_OPERATORS^
6146 @emph{Check Boolean operators.}
6147 The use of AND/OR operators is not permitted except in the cases of modular
6148 operands, array operands, and simple stand-alone boolean variables or
6149 boolean constants. In all other cases AND THEN/OR ELSE are required.
6152 @emph{Check comments.}
6153 Comments must meet the following set of rules:
6158 The ``@code{--}'' that starts the column must either start in column one,
6159 or else at least one blank must precede this sequence.
6162 Comments that follow other tokens on a line must have at least one blank
6163 following the ``@code{--}'' at the start of the comment.
6166 Full line comments must have two blanks following the ``@code{--}'' that
6167 starts the comment, with the following exceptions.
6170 A line consisting only of the ``@code{--}'' characters, possibly preceded
6171 by blanks is permitted.
6174 A comment starting with ``@code{--x}'' where @code{x} is a special character
6176 This allows proper processing of the output generated by specialized tools
6177 including @command{gnatprep} (where ``@code{--!}'' is used) and the SPARK
6179 language (where ``@code{--#}'' is used). For the purposes of this rule, a
6180 special character is defined as being in one of the ASCII ranges
6181 @code{16#21#@dots{}16#2F#} or @code{16#3A#@dots{}16#3F#}.
6182 Note that this usage is not permitted
6183 in GNAT implementation units (i.e., when @option{-gnatg} is used).
6186 A line consisting entirely of minus signs, possibly preceded by blanks, is
6187 permitted. This allows the construction of box comments where lines of minus
6188 signs are used to form the top and bottom of the box.
6191 A comment that starts and ends with ``@code{--}'' is permitted as long as at
6192 least one blank follows the initial ``@code{--}''. Together with the preceding
6193 rule, this allows the construction of box comments, as shown in the following
6196 ---------------------------
6197 -- This is a box comment --
6198 -- with two text lines. --
6199 ---------------------------
6203 @item ^d^DOS_LINE_ENDINGS^
6204 @emph{Check no DOS line terminators present.}
6205 All lines must be terminated by a single ASCII.LF
6206 character (in particular the DOS line terminator sequence CR/LF is not
6210 @emph{Check end/exit labels.}
6211 Optional labels on @code{end} statements ending subprograms and on
6212 @code{exit} statements exiting named loops, are required to be present.
6215 @emph{No form feeds or vertical tabs.}
6216 Neither form feeds nor vertical tab characters are permitted
6220 @emph{GNAT style mode}
6221 The set of style check switches is set to match that used by the GNAT sources.
6222 This may be useful when developing code that is eventually intended to be
6223 incorporated into GNAT. For further details, see GNAT sources.
6226 @emph{No horizontal tabs.}
6227 Horizontal tab characters are not permitted in the source text.
6228 Together with the b (no blanks at end of line) check, this
6229 enforces a canonical form for the use of blanks to separate
6233 @emph{Check if-then layout.}
6234 The keyword @code{then} must appear either on the same
6235 line as corresponding @code{if}, or on a line on its own, lined
6236 up under the @code{if} with at least one non-blank line in between
6237 containing all or part of the condition to be tested.
6240 @emph{check mode IN keywords}
6241 Mode @code{in} (the default mode) is not
6242 allowed to be given explicitly. @code{in out} is fine,
6243 but not @code{in} on its own.
6246 @emph{Check keyword casing.}
6247 All keywords must be in lower case (with the exception of keywords
6248 such as @code{digits} used as attribute names to which this check
6252 @emph{Check layout.}
6253 Layout of statement and declaration constructs must follow the
6254 recommendations in the Ada Reference Manual, as indicated by the
6255 form of the syntax rules. For example an @code{else} keyword must
6256 be lined up with the corresponding @code{if} keyword.
6258 There are two respects in which the style rule enforced by this check
6259 option are more liberal than those in the Ada Reference Manual. First
6260 in the case of record declarations, it is permissible to put the
6261 @code{record} keyword on the same line as the @code{type} keyword, and
6262 then the @code{end} in @code{end record} must line up under @code{type}.
6263 This is also permitted when the type declaration is split on two lines.
6264 For example, any of the following three layouts is acceptable:
6266 @smallexample @c ada
6289 Second, in the case of a block statement, a permitted alternative
6290 is to put the block label on the same line as the @code{declare} or
6291 @code{begin} keyword, and then line the @code{end} keyword up under
6292 the block label. For example both the following are permitted:
6294 @smallexample @c ada
6312 The same alternative format is allowed for loops. For example, both of
6313 the following are permitted:
6315 @smallexample @c ada
6317 Clear : while J < 10 loop
6328 @item ^Lnnn^MAX_NESTING=nnn^
6329 @emph{Set maximum nesting level}
6330 The maximum level of nesting of constructs (including subprograms, loops,
6331 blocks, packages, and conditionals) may not exceed the given value
6332 @option{nnn}. A value of zero disconnects this style check.
6334 @item ^m^LINE_LENGTH^
6335 @emph{Check maximum line length.}
6336 The length of source lines must not exceed 79 characters, including
6337 any trailing blanks. The value of 79 allows convenient display on an
6338 80 character wide device or window, allowing for possible special
6339 treatment of 80 character lines. Note that this count is of
6340 characters in the source text. This means that a tab character counts
6341 as one character in this count but a wide character sequence counts as
6342 a single character (however many bytes are needed in the encoding).
6344 @item ^Mnnn^MAX_LENGTH=nnn^
6345 @emph{Set maximum line length.}
6346 The length of lines must not exceed the
6347 given value @option{nnn}. The maximum value that can be specified is 32767.
6349 @item ^n^STANDARD_CASING^
6350 @emph{Check casing of entities in Standard.}
6351 Any identifier from Standard must be cased
6352 to match the presentation in the Ada Reference Manual (for example,
6353 @code{Integer} and @code{ASCII.NUL}).
6356 @emph{Turn off all style checks}
6357 All style check options are turned off.
6359 @item ^o^ORDERED_SUBPROGRAMS^
6360 @emph{Check order of subprogram bodies.}
6361 All subprogram bodies in a given scope
6362 (e.g.@: a package body) must be in alphabetical order. The ordering
6363 rule uses normal Ada rules for comparing strings, ignoring casing
6364 of letters, except that if there is a trailing numeric suffix, then
6365 the value of this suffix is used in the ordering (e.g.@: Junk2 comes
6368 @item ^O^OVERRIDING_INDICATORS^
6369 @emph{Check that overriding subprograms are explicitly marked as such.}
6370 The declaration of a primitive operation of a type extension that overrides
6371 an inherited operation must carry an overriding indicator.
6374 @emph{Check pragma casing.}
6375 Pragma names must be written in mixed case, that is, the
6376 initial letter and any letter following an underscore must be uppercase.
6377 All other letters must be lowercase.
6379 @item ^r^REFERENCES^
6380 @emph{Check references.}
6381 All identifier references must be cased in the same way as the
6382 corresponding declaration. No specific casing style is imposed on
6383 identifiers. The only requirement is for consistency of references
6386 @item ^S^STATEMENTS_AFTER_THEN_ELSE^
6387 @emph{Check no statements after THEN/ELSE.}
6388 No statements are allowed
6389 on the same line as a THEN or ELSE keyword following the
6390 keyword in an IF statement. OR ELSE and AND THEN are not affected,
6391 and a special exception allows a pragma to appear after ELSE.
6394 @emph{Check separate specs.}
6395 Separate declarations (``specs'') are required for subprograms (a
6396 body is not allowed to serve as its own declaration). The only
6397 exception is that parameterless library level procedures are
6398 not required to have a separate declaration. This exception covers
6399 the most frequent form of main program procedures.
6402 @emph{Check token spacing.}
6403 The following token spacing rules are enforced:
6408 The keywords @code{@b{abs}} and @code{@b{not}} must be followed by a space.
6411 The token @code{=>} must be surrounded by spaces.
6414 The token @code{<>} must be preceded by a space or a left parenthesis.
6417 Binary operators other than @code{**} must be surrounded by spaces.
6418 There is no restriction on the layout of the @code{**} binary operator.
6421 Colon must be surrounded by spaces.
6424 Colon-equal (assignment, initialization) must be surrounded by spaces.
6427 Comma must be the first non-blank character on the line, or be
6428 immediately preceded by a non-blank character, and must be followed
6432 If the token preceding a left parenthesis ends with a letter or digit, then
6433 a space must separate the two tokens.
6436 A right parenthesis must either be the first non-blank character on
6437 a line, or it must be preceded by a non-blank character.
6440 A semicolon must not be preceded by a space, and must not be followed by
6441 a non-blank character.
6444 A unary plus or minus may not be followed by a space.
6447 A vertical bar must be surrounded by spaces.
6450 @item ^u^UNNECESSARY_BLANK_LINES^
6451 @emph{Check unnecessary blank lines.}
6452 Unnecessary blank lines are not allowed. A blank line is considered
6453 unnecessary if it appears at the end of the file, or if more than
6454 one blank line occurs in sequence.
6456 @item ^x^XTRA_PARENS^
6457 @emph{Check extra parentheses.}
6458 Unnecessary extra level of parentheses (C-style) are not allowed
6459 around conditions in @code{if} statements, @code{while} statements and
6460 @code{exit} statements.
6462 @item ^y^ALL_BUILTIN^
6463 @emph{Set all standard style check options}
6464 This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking
6465 options enabled with the exception of @option{-gnatyo}, @option{-gnatyI},
6466 @option{-gnatyS}, @option{-gnatyLnnn},
6467 @option{-gnatyd}, @option{-gnatyu}, and @option{-gnatyx}.
6471 @emph{Remove style check options}
6472 This causes any subsequent options in the string to act as canceling the
6473 corresponding style check option. To cancel maximum nesting level control,
6474 use @option{L} parameter witout any integer value after that, because any
6475 digit following @option{-} in the parameter string of the @option{-gnaty}
6476 option will be threated as canceling indentation check. The same is true
6477 for @option{M} parameter. @option{y} and @option{N} parameters are not
6478 allowed after @option{-}.
6481 This causes any subsequent options in the string to enable the corresponding
6482 style check option. That is, it cancels the effect of a previous ^-^REMOVE^,
6488 @emph{Removing style check options}
6489 If the name of a style check is preceded by @option{NO} then the corresponding
6490 style check is turned off. For example @option{NOCOMMENTS} turns off style
6491 checking for comments.
6496 In the above rules, appearing in column one is always permitted, that is,
6497 counts as meeting either a requirement for a required preceding space,
6498 or as meeting a requirement for no preceding space.
6500 Appearing at the end of a line is also always permitted, that is, counts
6501 as meeting either a requirement for a following space, or as meeting
6502 a requirement for no following space.
6505 If any of these style rules is violated, a message is generated giving
6506 details on the violation. The initial characters of such messages are
6507 always ``@code{(style)}''. Note that these messages are treated as warning
6508 messages, so they normally do not prevent the generation of an object
6509 file. The @option{-gnatwe} switch can be used to treat warning messages,
6510 including style messages, as fatal errors.
6514 @option{-gnaty} on its own (that is not
6515 followed by any letters or digits), then the effect is equivalent
6516 to the use of @option{-gnatyy}, as described above, that is all
6517 built-in standard style check options are enabled.
6521 /STYLE_CHECKS=ALL_BUILTIN enables all checking options with
6522 the exception of ORDERED_SUBPROGRAMS, UNNECESSARY_BLANK_LINES,
6523 XTRA_PARENS, and DOS_LINE_ENDINGS. In addition
6535 clears any previously set style checks.
6537 @node Run-Time Checks
6538 @subsection Run-Time Checks
6539 @cindex Division by zero
6540 @cindex Access before elaboration
6541 @cindex Checks, division by zero
6542 @cindex Checks, access before elaboration
6543 @cindex Checks, stack overflow checking
6546 By default, the following checks are suppressed: integer overflow
6547 checks, stack overflow checks, and checks for access before
6548 elaboration on subprogram calls. All other checks, including range
6549 checks and array bounds checks, are turned on by default. The
6550 following @command{gcc} switches refine this default behavior.
6555 @cindex @option{-gnatp} (@command{gcc})
6556 @cindex Suppressing checks
6557 @cindex Checks, suppressing
6559 This switch causes the unit to be compiled
6560 as though @code{pragma Suppress (All_checks)}
6561 had been present in the source. Validity checks are also eliminated (in
6562 other words @option{-gnatp} also implies @option{-gnatVn}.
6563 Use this switch to improve the performance
6564 of the code at the expense of safety in the presence of invalid data or
6567 Note that when checks are suppressed, the compiler is allowed, but not
6568 required, to omit the checking code. If the run-time cost of the
6569 checking code is zero or near-zero, the compiler will generate it even
6570 if checks are suppressed. In particular, if the compiler can prove
6571 that a certain check will necessarily fail, it will generate code to
6572 do an unconditional ``raise'', even if checks are suppressed. The
6573 compiler warns in this case. Another case in which checks may not be
6574 eliminated is when they are embedded in certain run time routines such
6575 as math library routines.
6577 Of course, run-time checks are omitted whenever the compiler can prove
6578 that they will not fail, whether or not checks are suppressed.
6580 Note that if you suppress a check that would have failed, program
6581 execution is erroneous, which means the behavior is totally
6582 unpredictable. The program might crash, or print wrong answers, or
6583 do anything else. It might even do exactly what you wanted it to do
6584 (and then it might start failing mysteriously next week or next
6585 year). The compiler will generate code based on the assumption that
6586 the condition being checked is true, which can result in disaster if
6587 that assumption is wrong.
6590 @cindex @option{-gnato} (@command{gcc})
6591 @cindex Overflow checks
6592 @cindex Check, overflow
6593 Enables overflow checking for integer operations.
6594 This causes GNAT to generate slower and larger executable
6595 programs by adding code to check for overflow (resulting in raising
6596 @code{Constraint_Error} as required by standard Ada
6597 semantics). These overflow checks correspond to situations in which
6598 the true value of the result of an operation may be outside the base
6599 range of the result type. The following example shows the distinction:
6601 @smallexample @c ada
6602 X1 : Integer := "Integer'Last";
6603 X2 : Integer range 1 .. 5 := "5";
6604 X3 : Integer := "Integer'Last";
6605 X4 : Integer range 1 .. 5 := "5";
6606 F : Float := "2.0E+20";
6615 Note that if explicit values are assigned at compile time, the
6616 compiler may be able to detect overflow at compile time, in which case
6617 no actual run-time checking code is required, and Constraint_Error
6618 will be raised unconditionally, with or without
6619 @option{-gnato}. That's why the assigned values in the above fragment
6620 are in quotes, the meaning is "assign a value not known to the
6621 compiler that happens to be equal to ...". The remaining discussion
6622 assumes that the compiler cannot detect the values at compile time.
6624 Here the first addition results in a value that is outside the base range
6625 of Integer, and hence requires an overflow check for detection of the
6626 constraint error. Thus the first assignment to @code{X1} raises a
6627 @code{Constraint_Error} exception only if @option{-gnato} is set.
6629 The second increment operation results in a violation of the explicit
6630 range constraint; such range checks are performed by default, and are
6631 unaffected by @option{-gnato}.
6633 The two conversions of @code{F} both result in values that are outside
6634 the base range of type @code{Integer} and thus will raise
6635 @code{Constraint_Error} exceptions only if @option{-gnato} is used.
6636 The fact that the result of the second conversion is assigned to
6637 variable @code{X4} with a restricted range is irrelevant, since the problem
6638 is in the conversion, not the assignment.
6640 Basically the rule is that in the default mode (@option{-gnato} not
6641 used), the generated code assures that all integer variables stay
6642 within their declared ranges, or within the base range if there is
6643 no declared range. This prevents any serious problems like indexes
6644 out of range for array operations.
6646 What is not checked in default mode is an overflow that results in
6647 an in-range, but incorrect value. In the above example, the assignments
6648 to @code{X1}, @code{X2}, @code{X3} all give results that are within the
6649 range of the target variable, but the result is wrong in the sense that
6650 it is too large to be represented correctly. Typically the assignment
6651 to @code{X1} will result in wrap around to the largest negative number.
6652 The conversions of @code{F} will result in some @code{Integer} value
6653 and if that integer value is out of the @code{X4} range then the
6654 subsequent assignment would generate an exception.
6656 @findex Machine_Overflows
6657 Note that the @option{-gnato} switch does not affect the code generated
6658 for any floating-point operations; it applies only to integer
6660 For floating-point, GNAT has the @code{Machine_Overflows}
6661 attribute set to @code{False} and the normal mode of operation is to
6662 generate IEEE NaN and infinite values on overflow or invalid operations
6663 (such as dividing 0.0 by 0.0).
6665 The reason that we distinguish overflow checking from other kinds of
6666 range constraint checking is that a failure of an overflow check, unlike
6667 for example the failure of a range check, can result in an incorrect
6668 value, but cannot cause random memory destruction (like an out of range
6669 subscript), or a wild jump (from an out of range case value). Overflow
6670 checking is also quite expensive in time and space, since in general it
6671 requires the use of double length arithmetic.
6673 Note again that @option{-gnato} is off by default, so overflow checking is
6674 not performed in default mode. This means that out of the box, with the
6675 default settings, GNAT does not do all the checks expected from the
6676 language description in the Ada Reference Manual. If you want all constraint
6677 checks to be performed, as described in this Manual, then you must
6678 explicitly use the -gnato switch either on the @command{gnatmake} or
6679 @command{gcc} command.
6682 @cindex @option{-gnatE} (@command{gcc})
6683 @cindex Elaboration checks
6684 @cindex Check, elaboration
6685 Enables dynamic checks for access-before-elaboration
6686 on subprogram calls and generic instantiations.
6687 Note that @option{-gnatE} is not necessary for safety, because in the
6688 default mode, GNAT ensures statically that the checks would not fail.
6689 For full details of the effect and use of this switch,
6690 @xref{Compiling Using gcc}.
6693 @cindex @option{-fstack-check} (@command{gcc})
6694 @cindex Stack Overflow Checking
6695 @cindex Checks, stack overflow checking
6696 Activates stack overflow checking. For full details of the effect and use of
6697 this switch see @ref{Stack Overflow Checking}.
6702 The setting of these switches only controls the default setting of the
6703 checks. You may modify them using either @code{Suppress} (to remove
6704 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
6707 @node Using gcc for Syntax Checking
6708 @subsection Using @command{gcc} for Syntax Checking
6711 @cindex @option{-gnats} (@command{gcc})
6715 The @code{s} stands for ``syntax''.
6718 Run GNAT in syntax checking only mode. For
6719 example, the command
6722 $ gcc -c -gnats x.adb
6726 compiles file @file{x.adb} in syntax-check-only mode. You can check a
6727 series of files in a single command
6729 , and can use wild cards to specify such a group of files.
6730 Note that you must specify the @option{-c} (compile
6731 only) flag in addition to the @option{-gnats} flag.
6734 You may use other switches in conjunction with @option{-gnats}. In
6735 particular, @option{-gnatl} and @option{-gnatv} are useful to control the
6736 format of any generated error messages.
6738 When the source file is empty or contains only empty lines and/or comments,
6739 the output is a warning:
6742 $ gcc -c -gnats -x ada toto.txt
6743 toto.txt:1:01: warning: empty file, contains no compilation units
6747 Otherwise, the output is simply the error messages, if any. No object file or
6748 ALI file is generated by a syntax-only compilation. Also, no units other
6749 than the one specified are accessed. For example, if a unit @code{X}
6750 @code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax
6751 check only mode does not access the source file containing unit
6754 @cindex Multiple units, syntax checking
6755 Normally, GNAT allows only a single unit in a source file. However, this
6756 restriction does not apply in syntax-check-only mode, and it is possible
6757 to check a file containing multiple compilation units concatenated
6758 together. This is primarily used by the @code{gnatchop} utility
6759 (@pxref{Renaming Files Using gnatchop}).
6762 @node Using gcc for Semantic Checking
6763 @subsection Using @command{gcc} for Semantic Checking
6766 @cindex @option{-gnatc} (@command{gcc})
6770 The @code{c} stands for ``check''.
6772 Causes the compiler to operate in semantic check mode,
6773 with full checking for all illegalities specified in the
6774 Ada Reference Manual, but without generation of any object code
6775 (no object file is generated).
6777 Because dependent files must be accessed, you must follow the GNAT
6778 semantic restrictions on file structuring to operate in this mode:
6782 The needed source files must be accessible
6783 (@pxref{Search Paths and the Run-Time Library (RTL)}).
6786 Each file must contain only one compilation unit.
6789 The file name and unit name must match (@pxref{File Naming Rules}).
6792 The output consists of error messages as appropriate. No object file is
6793 generated. An @file{ALI} file is generated for use in the context of
6794 cross-reference tools, but this file is marked as not being suitable
6795 for binding (since no object file is generated).
6796 The checking corresponds exactly to the notion of
6797 legality in the Ada Reference Manual.
6799 Any unit can be compiled in semantics-checking-only mode, including
6800 units that would not normally be compiled (subunits,
6801 and specifications where a separate body is present).
6804 @node Compiling Different Versions of Ada
6805 @subsection Compiling Different Versions of Ada
6808 The switches described in this section allow you to explicitly specify
6809 the version of the Ada language that your programs are written in.
6810 By default @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
6811 but you can also specify @value{NONDEFAULTLANGUAGEVERSION} or
6812 indicate Ada 83 compatibility mode.
6815 @cindex Compatibility with Ada 83
6817 @item -gnat83 (Ada 83 Compatibility Mode)
6818 @cindex @option{-gnat83} (@command{gcc})
6819 @cindex ACVC, Ada 83 tests
6823 Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch
6824 specifies that the program is to be compiled in Ada 83 mode. With
6825 @option{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83
6826 semantics where this can be done easily.
6827 It is not possible to guarantee this switch does a perfect
6828 job; some subtle tests, such as are
6829 found in earlier ACVC tests (and that have been removed from the ACATS suite
6830 for Ada 95), might not compile correctly.
6831 Nevertheless, this switch may be useful in some circumstances, for example
6832 where, due to contractual reasons, existing code needs to be maintained
6833 using only Ada 83 features.
6835 With few exceptions (most notably the need to use @code{<>} on
6836 @cindex Generic formal parameters
6837 unconstrained generic formal parameters, the use of the new Ada 95 / Ada 2005
6838 reserved words, and the use of packages
6839 with optional bodies), it is not necessary to specify the
6840 @option{-gnat83} switch when compiling Ada 83 programs, because, with rare
6841 exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus
6842 a correct Ada 83 program is usually also a correct program
6843 in these later versions of the language standard.
6844 For further information, please refer to @ref{Compatibility and Porting Guide}.
6846 @item -gnat95 (Ada 95 mode)
6847 @cindex @option{-gnat95} (@command{gcc})
6851 This switch directs the compiler to implement the Ada 95 version of the
6853 Since Ada 95 is almost completely upwards
6854 compatible with Ada 83, Ada 83 programs may generally be compiled using
6855 this switch (see the description of the @option{-gnat83} switch for further
6856 information about Ada 83 mode).
6857 If an Ada 2005 program is compiled in Ada 95 mode,
6858 uses of the new Ada 2005 features will cause error
6859 messages or warnings.
6861 This switch also can be used to cancel the effect of a previous
6862 @option{-gnat83} or @option{-gnat05} switch earlier in the command line.
6864 @item -gnat05 (Ada 2005 mode)
6865 @cindex @option{-gnat05} (@command{gcc})
6866 @cindex Ada 2005 mode
6869 This switch directs the compiler to implement the Ada 2005 version of the
6871 Since Ada 2005 is almost completely upwards
6872 compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
6873 may generally be compiled using this switch (see the description of the
6874 @option{-gnat83} and @option{-gnat95} switches for further
6877 For information about the approved ``Ada Issues'' that have been incorporated
6878 into Ada 2005, see @url{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/AIs}.
6879 Included with GNAT releases is a file @file{features-ada0y} that describes
6880 the set of implemented Ada 2005 features.
6884 @node Character Set Control
6885 @subsection Character Set Control
6887 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
6888 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
6891 Normally GNAT recognizes the Latin-1 character set in source program
6892 identifiers, as described in the Ada Reference Manual.
6894 GNAT to recognize alternate character sets in identifiers. @var{c} is a
6895 single character ^^or word^ indicating the character set, as follows:
6899 ISO 8859-1 (Latin-1) identifiers
6902 ISO 8859-2 (Latin-2) letters allowed in identifiers
6905 ISO 8859-3 (Latin-3) letters allowed in identifiers
6908 ISO 8859-4 (Latin-4) letters allowed in identifiers
6911 ISO 8859-5 (Cyrillic) letters allowed in identifiers
6914 ISO 8859-15 (Latin-9) letters allowed in identifiers
6917 IBM PC letters (code page 437) allowed in identifiers
6920 IBM PC letters (code page 850) allowed in identifiers
6922 @item ^f^FULL_UPPER^
6923 Full upper-half codes allowed in identifiers
6926 No upper-half codes allowed in identifiers
6929 Wide-character codes (that is, codes greater than 255)
6930 allowed in identifiers
6933 @xref{Foreign Language Representation}, for full details on the
6934 implementation of these character sets.
6936 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
6937 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
6938 Specify the method of encoding for wide characters.
6939 @var{e} is one of the following:
6944 Hex encoding (brackets coding also recognized)
6947 Upper half encoding (brackets encoding also recognized)
6950 Shift/JIS encoding (brackets encoding also recognized)
6953 EUC encoding (brackets encoding also recognized)
6956 UTF-8 encoding (brackets encoding also recognized)
6959 Brackets encoding only (default value)
6961 For full details on these encoding
6962 methods see @ref{Wide Character Encodings}.
6963 Note that brackets coding is always accepted, even if one of the other
6964 options is specified, so for example @option{-gnatW8} specifies that both
6965 brackets and UTF-8 encodings will be recognized. The units that are
6966 with'ed directly or indirectly will be scanned using the specified
6967 representation scheme, and so if one of the non-brackets scheme is
6968 used, it must be used consistently throughout the program. However,
6969 since brackets encoding is always recognized, it may be conveniently
6970 used in standard libraries, allowing these libraries to be used with
6971 any of the available coding schemes.
6974 If no @option{-gnatW?} parameter is present, then the default
6975 representation is normally Brackets encoding only. However, if the
6976 first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard
6977 byte order mark or BOM for UTF-8), then these three characters are
6978 skipped and the default representation for the file is set to UTF-8.
6980 Note that the wide character representation that is specified (explicitly
6981 or by default) for the main program also acts as the default encoding used
6982 for Wide_Text_IO files if not specifically overridden by a WCEM form
6986 @node File Naming Control
6987 @subsection File Naming Control
6990 @item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
6991 @cindex @option{-gnatk} (@command{gcc})
6992 Activates file name ``krunching''. @var{n}, a decimal integer in the range
6993 1-999, indicates the maximum allowable length of a file name (not
6994 including the @file{.ads} or @file{.adb} extension). The default is not
6995 to enable file name krunching.
6997 For the source file naming rules, @xref{File Naming Rules}.
7000 @node Subprogram Inlining Control
7001 @subsection Subprogram Inlining Control
7006 @cindex @option{-gnatn} (@command{gcc})
7008 The @code{n} here is intended to suggest the first syllable of the
7011 GNAT recognizes and processes @code{Inline} pragmas. However, for the
7012 inlining to actually occur, optimization must be enabled. To enable
7013 inlining of subprograms specified by pragma @code{Inline},
7014 you must also specify this switch.
7015 In the absence of this switch, GNAT does not attempt
7016 inlining and does not need to access the bodies of
7017 subprograms for which @code{pragma Inline} is specified if they are not
7018 in the current unit.
7020 If you specify this switch the compiler will access these bodies,
7021 creating an extra source dependency for the resulting object file, and
7022 where possible, the call will be inlined.
7023 For further details on when inlining is possible
7024 see @ref{Inlining of Subprograms}.
7027 @cindex @option{-gnatN} (@command{gcc})
7028 This switch activates front-end inlining which also
7029 generates additional dependencies.
7031 When using a gcc-based back end (in practice this means using any version
7032 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
7033 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
7034 Historically front end inlining was more extensive than the gcc back end
7035 inlining, but that is no longer the case.
7038 @node Auxiliary Output Control
7039 @subsection Auxiliary Output Control
7043 @cindex @option{-gnatt} (@command{gcc})
7044 @cindex Writing internal trees
7045 @cindex Internal trees, writing to file
7046 Causes GNAT to write the internal tree for a unit to a file (with the
7047 extension @file{.adt}.
7048 This not normally required, but is used by separate analysis tools.
7050 these tools do the necessary compilations automatically, so you should
7051 not have to specify this switch in normal operation.
7052 Note that the combination of switches @option{-gnatct}
7053 generates a tree in the form required by ASIS applications.
7056 @cindex @option{-gnatu} (@command{gcc})
7057 Print a list of units required by this compilation on @file{stdout}.
7058 The listing includes all units on which the unit being compiled depends
7059 either directly or indirectly.
7062 @item -pass-exit-codes
7063 @cindex @option{-pass-exit-codes} (@command{gcc})
7064 If this switch is not used, the exit code returned by @command{gcc} when
7065 compiling multiple files indicates whether all source files have
7066 been successfully used to generate object files or not.
7068 When @option{-pass-exit-codes} is used, @command{gcc} exits with an extended
7069 exit status and allows an integrated development environment to better
7070 react to a compilation failure. Those exit status are:
7074 There was an error in at least one source file.
7076 At least one source file did not generate an object file.
7078 The compiler died unexpectedly (internal error for example).
7080 An object file has been generated for every source file.
7085 @node Debugging Control
7086 @subsection Debugging Control
7090 @cindex Debugging options
7093 @cindex @option{-gnatd} (@command{gcc})
7094 Activate internal debugging switches. @var{x} is a letter or digit, or
7095 string of letters or digits, which specifies the type of debugging
7096 outputs desired. Normally these are used only for internal development
7097 or system debugging purposes. You can find full documentation for these
7098 switches in the body of the @code{Debug} unit in the compiler source
7099 file @file{debug.adb}.
7103 @cindex @option{-gnatG} (@command{gcc})
7104 This switch causes the compiler to generate auxiliary output containing
7105 a pseudo-source listing of the generated expanded code. Like most Ada
7106 compilers, GNAT works by first transforming the high level Ada code into
7107 lower level constructs. For example, tasking operations are transformed
7108 into calls to the tasking run-time routines. A unique capability of GNAT
7109 is to list this expanded code in a form very close to normal Ada source.
7110 This is very useful in understanding the implications of various Ada
7111 usage on the efficiency of the generated code. There are many cases in
7112 Ada (e.g.@: the use of controlled types), where simple Ada statements can
7113 generate a lot of run-time code. By using @option{-gnatG} you can identify
7114 these cases, and consider whether it may be desirable to modify the coding
7115 approach to improve efficiency.
7117 The optional parameter @code{nn} if present after -gnatG specifies an
7118 alternative maximum line length that overrides the normal default of 72.
7119 This value is in the range 40-999999, values less than 40 being silently
7120 reset to 40. The equal sign is optional.
7122 The format of the output is very similar to standard Ada source, and is
7123 easily understood by an Ada programmer. The following special syntactic
7124 additions correspond to low level features used in the generated code that
7125 do not have any exact analogies in pure Ada source form. The following
7126 is a partial list of these special constructions. See the spec
7127 of package @code{Sprint} in file @file{sprint.ads} for a full list.
7129 If the switch @option{-gnatL} is used in conjunction with
7130 @cindex @option{-gnatL} (@command{gcc})
7131 @option{-gnatG}, then the original source lines are interspersed
7132 in the expanded source (as comment lines with the original line number).
7135 @item new @var{xxx} @r{[}storage_pool = @var{yyy}@r{]}
7136 Shows the storage pool being used for an allocator.
7138 @item at end @var{procedure-name};
7139 Shows the finalization (cleanup) procedure for a scope.
7141 @item (if @var{expr} then @var{expr} else @var{expr})
7142 Conditional expression equivalent to the @code{x?y:z} construction in C.
7144 @item @var{target}^^^(@var{source})
7145 A conversion with floating-point truncation instead of rounding.
7147 @item @var{target}?(@var{source})
7148 A conversion that bypasses normal Ada semantic checking. In particular
7149 enumeration types and fixed-point types are treated simply as integers.
7151 @item @var{target}?^^^(@var{source})
7152 Combines the above two cases.
7154 @item @var{x} #/ @var{y}
7155 @itemx @var{x} #mod @var{y}
7156 @itemx @var{x} #* @var{y}
7157 @itemx @var{x} #rem @var{y}
7158 A division or multiplication of fixed-point values which are treated as
7159 integers without any kind of scaling.
7161 @item free @var{expr} @r{[}storage_pool = @var{xxx}@r{]}
7162 Shows the storage pool associated with a @code{free} statement.
7164 @item [subtype or type declaration]
7165 Used to list an equivalent declaration for an internally generated
7166 type that is referenced elsewhere in the listing.
7168 @item freeze @var{type-name} @ovar{actions}
7169 Shows the point at which @var{type-name} is frozen, with possible
7170 associated actions to be performed at the freeze point.
7172 @item reference @var{itype}
7173 Reference (and hence definition) to internal type @var{itype}.
7175 @item @var{function-name}! (@var{arg}, @var{arg}, @var{arg})
7176 Intrinsic function call.
7178 @item @var{label-name} : label
7179 Declaration of label @var{labelname}.
7181 @item #$ @var{subprogram-name}
7182 An implicit call to a run-time support routine
7183 (to meet the requirement of H.3.1(9) in a
7186 @item @var{expr} && @var{expr} && @var{expr} @dots{} && @var{expr}
7187 A multiple concatenation (same effect as @var{expr} & @var{expr} &
7188 @var{expr}, but handled more efficiently).
7190 @item [constraint_error]
7191 Raise the @code{Constraint_Error} exception.
7193 @item @var{expression}'reference
7194 A pointer to the result of evaluating @var{expression}.
7196 @item @var{target-type}!(@var{source-expression})
7197 An unchecked conversion of @var{source-expression} to @var{target-type}.
7199 @item [@var{numerator}/@var{denominator}]
7200 Used to represent internal real literals (that) have no exact
7201 representation in base 2-16 (for example, the result of compile time
7202 evaluation of the expression 1.0/27.0).
7206 @cindex @option{-gnatD} (@command{gcc})
7207 When used in conjunction with @option{-gnatG}, this switch causes
7208 the expanded source, as described above for
7209 @option{-gnatG} to be written to files with names
7210 @file{^xxx.dg^XXX_DG^}, where @file{xxx} is the normal file name,
7211 instead of to the standard output file. For
7212 example, if the source file name is @file{hello.adb}, then a file
7213 @file{^hello.adb.dg^HELLO.ADB_DG^} will be written. The debugging
7214 information generated by the @command{gcc} @option{^-g^/DEBUG^} switch
7215 will refer to the generated @file{^xxx.dg^XXX_DG^} file. This allows
7216 you to do source level debugging using the generated code which is
7217 sometimes useful for complex code, for example to find out exactly
7218 which part of a complex construction raised an exception. This switch
7219 also suppress generation of cross-reference information (see
7220 @option{-gnatx}) since otherwise the cross-reference information
7221 would refer to the @file{^.dg^.DG^} file, which would cause
7222 confusion since this is not the original source file.
7224 Note that @option{-gnatD} actually implies @option{-gnatG}
7225 automatically, so it is not necessary to give both options.
7226 In other words @option{-gnatD} is equivalent to @option{-gnatDG}).
7228 If the switch @option{-gnatL} is used in conjunction with
7229 @cindex @option{-gnatL} (@command{gcc})
7230 @option{-gnatDG}, then the original source lines are interspersed
7231 in the expanded source (as comment lines with the original line number).
7233 The optional parameter @code{nn} if present after -gnatD specifies an
7234 alternative maximum line length that overrides the normal default of 72.
7235 This value is in the range 40-999999, values less than 40 being silently
7236 reset to 40. The equal sign is optional.
7239 @cindex @option{-gnatr} (@command{gcc})
7240 @cindex pragma Restrictions
7241 This switch causes pragma Restrictions to be treated as Restriction_Warnings
7242 so that violation of restrictions causes warnings rather than illegalities.
7243 This is useful during the development process when new restrictions are added
7244 or investigated. The switch also causes pragma Profile to be treated as
7245 Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set
7246 restriction warnings rather than restrictions.
7249 @item -gnatR@r{[}0@r{|}1@r{|}2@r{|}3@r{[}s@r{]]}
7250 @cindex @option{-gnatR} (@command{gcc})
7251 This switch controls output from the compiler of a listing showing
7252 representation information for declared types and objects. For
7253 @option{-gnatR0}, no information is output (equivalent to omitting
7254 the @option{-gnatR} switch). For @option{-gnatR1} (which is the default,
7255 so @option{-gnatR} with no parameter has the same effect), size and alignment
7256 information is listed for declared array and record types. For
7257 @option{-gnatR2}, size and alignment information is listed for all
7258 declared types and objects. Finally @option{-gnatR3} includes symbolic
7259 expressions for values that are computed at run time for
7260 variant records. These symbolic expressions have a mostly obvious
7261 format with #n being used to represent the value of the n'th
7262 discriminant. See source files @file{repinfo.ads/adb} in the
7263 @code{GNAT} sources for full details on the format of @option{-gnatR3}
7264 output. If the switch is followed by an s (e.g.@: @option{-gnatR2s}), then
7265 the output is to a file with the name @file{^file.rep^file_REP^} where
7266 file is the name of the corresponding source file.
7269 @item /REPRESENTATION_INFO
7270 @cindex @option{/REPRESENTATION_INFO} (@command{gcc})
7271 This qualifier controls output from the compiler of a listing showing
7272 representation information for declared types and objects. For
7273 @option{/REPRESENTATION_INFO=NONE}, no information is output
7274 (equivalent to omitting the @option{/REPRESENTATION_INFO} qualifier).
7275 @option{/REPRESENTATION_INFO} without option is equivalent to
7276 @option{/REPRESENTATION_INFO=ARRAYS}.
7277 For @option{/REPRESENTATION_INFO=ARRAYS}, size and alignment
7278 information is listed for declared array and record types. For
7279 @option{/REPRESENTATION_INFO=OBJECTS}, size and alignment information
7280 is listed for all expression information for values that are computed
7281 at run time for variant records. These symbolic expressions have a mostly
7282 obvious format with #n being used to represent the value of the n'th
7283 discriminant. See source files @file{REPINFO.ADS/ADB} in the
7284 @code{GNAT} sources for full details on the format of
7285 @option{/REPRESENTATION_INFO=SYMBOLIC} output.
7286 If _FILE is added at the end of an option
7287 (e.g.@: @option{/REPRESENTATION_INFO=ARRAYS_FILE}),
7288 then the output is to a file with the name @file{file_REP} where
7289 file is the name of the corresponding source file.
7291 Note that it is possible for record components to have zero size. In
7292 this case, the component clause uses an obvious extension of permitted
7293 Ada syntax, for example @code{at 0 range 0 .. -1}.
7295 Representation information requires that code be generated (since it is the
7296 code generator that lays out complex data structures). If an attempt is made
7297 to output representation information when no code is generated, for example
7298 when a subunit is compiled on its own, then no information can be generated
7299 and the compiler outputs a message to this effect.
7302 @cindex @option{-gnatS} (@command{gcc})
7303 The use of the switch @option{-gnatS} for an
7304 Ada compilation will cause the compiler to output a
7305 representation of package Standard in a form very
7306 close to standard Ada. It is not quite possible to
7307 do this entirely in standard Ada (since new
7308 numeric base types cannot be created in standard
7309 Ada), but the output is easily
7310 readable to any Ada programmer, and is useful to
7311 determine the characteristics of target dependent
7312 types in package Standard.
7315 @cindex @option{-gnatx} (@command{gcc})
7316 Normally the compiler generates full cross-referencing information in
7317 the @file{ALI} file. This information is used by a number of tools,
7318 including @code{gnatfind} and @code{gnatxref}. The @option{-gnatx} switch
7319 suppresses this information. This saves some space and may slightly
7320 speed up compilation, but means that these tools cannot be used.
7323 @node Exception Handling Control
7324 @subsection Exception Handling Control
7327 GNAT uses two methods for handling exceptions at run-time. The
7328 @code{setjmp/longjmp} method saves the context when entering
7329 a frame with an exception handler. Then when an exception is
7330 raised, the context can be restored immediately, without the
7331 need for tracing stack frames. This method provides very fast
7332 exception propagation, but introduces significant overhead for
7333 the use of exception handlers, even if no exception is raised.
7335 The other approach is called ``zero cost'' exception handling.
7336 With this method, the compiler builds static tables to describe
7337 the exception ranges. No dynamic code is required when entering
7338 a frame containing an exception handler. When an exception is
7339 raised, the tables are used to control a back trace of the
7340 subprogram invocation stack to locate the required exception
7341 handler. This method has considerably poorer performance for
7342 the propagation of exceptions, but there is no overhead for
7343 exception handlers if no exception is raised. Note that in this
7344 mode and in the context of mixed Ada and C/C++ programming,
7345 to propagate an exception through a C/C++ code, the C/C++ code
7346 must be compiled with the @option{-funwind-tables} GCC's
7349 The following switches may be used to control which of the
7350 two exception handling methods is used.
7356 @cindex @option{--RTS=sjlj} (@command{gnatmake})
7357 This switch causes the setjmp/longjmp run-time (when available) to be used
7358 for exception handling. If the default
7359 mechanism for the target is zero cost exceptions, then
7360 this switch can be used to modify this default, and must be
7361 used for all units in the partition.
7362 This option is rarely used. One case in which it may be
7363 advantageous is if you have an application where exception
7364 raising is common and the overall performance of the
7365 application is improved by favoring exception propagation.
7368 @cindex @option{--RTS=zcx} (@command{gnatmake})
7369 @cindex Zero Cost Exceptions
7370 This switch causes the zero cost approach to be used
7371 for exception handling. If this is the default mechanism for the
7372 target (see below), then this switch is unneeded. If the default
7373 mechanism for the target is setjmp/longjmp exceptions, then
7374 this switch can be used to modify this default, and must be
7375 used for all units in the partition.
7376 This option can only be used if the zero cost approach
7377 is available for the target in use, otherwise it will generate an error.
7381 The same option @option{--RTS} must be used both for @command{gcc}
7382 and @command{gnatbind}. Passing this option to @command{gnatmake}
7383 (@pxref{Switches for gnatmake}) will ensure the required consistency
7384 through the compilation and binding steps.
7386 @node Units to Sources Mapping Files
7387 @subsection Units to Sources Mapping Files
7391 @item -gnatem^^=^@var{path}
7392 @cindex @option{-gnatem} (@command{gcc})
7393 A mapping file is a way to communicate to the compiler two mappings:
7394 from unit names to file names (without any directory information) and from
7395 file names to path names (with full directory information). These mappings
7396 are used by the compiler to short-circuit the path search.
7398 The use of mapping files is not required for correct operation of the
7399 compiler, but mapping files can improve efficiency, particularly when
7400 sources are read over a slow network connection. In normal operation,
7401 you need not be concerned with the format or use of mapping files,
7402 and the @option{-gnatem} switch is not a switch that you would use
7403 explicitly. it is intended only for use by automatic tools such as
7404 @command{gnatmake} running under the project file facility. The
7405 description here of the format of mapping files is provided
7406 for completeness and for possible use by other tools.
7408 A mapping file is a sequence of sets of three lines. In each set,
7409 the first line is the unit name, in lower case, with ``@code{%s}''
7411 specs and ``@code{%b}'' appended for bodies; the second line is the
7412 file name; and the third line is the path name.
7418 /gnat/project1/sources/main.2.ada
7421 When the switch @option{-gnatem} is specified, the compiler will create
7422 in memory the two mappings from the specified file. If there is any problem
7423 (nonexistent file, truncated file or duplicate entries), no mapping will
7426 Several @option{-gnatem} switches may be specified; however, only the last
7427 one on the command line will be taken into account.
7429 When using a project file, @command{gnatmake} create a temporary mapping file
7430 and communicates it to the compiler using this switch.
7434 @node Integrated Preprocessing
7435 @subsection Integrated Preprocessing
7438 GNAT sources may be preprocessed immediately before compilation.
7439 In this case, the actual
7440 text of the source is not the text of the source file, but is derived from it
7441 through a process called preprocessing. Integrated preprocessing is specified
7442 through switches @option{-gnatep} and/or @option{-gnateD}. @option{-gnatep}
7443 indicates, through a text file, the preprocessing data to be used.
7444 @option{-gnateD} specifies or modifies the values of preprocessing symbol.
7447 Note that when integrated preprocessing is used, the output from the
7448 preprocessor is not written to any external file. Instead it is passed
7449 internally to the compiler. If you need to preserve the result of
7450 preprocessing in a file, then you should use @command{gnatprep}
7451 to perform the desired preprocessing in stand-alone mode.
7454 It is recommended that @command{gnatmake} switch ^-s^/SWITCH_CHECK^ should be
7455 used when Integrated Preprocessing is used. The reason is that preprocessing
7456 with another Preprocessing Data file without changing the sources will
7457 not trigger recompilation without this switch.
7460 Note that @command{gnatmake} switch ^-m^/MINIMAL_RECOMPILATION^ will almost
7461 always trigger recompilation for sources that are preprocessed,
7462 because @command{gnatmake} cannot compute the checksum of the source after
7466 The actual preprocessing function is described in details in section
7467 @ref{Preprocessing Using gnatprep}. This section only describes how integrated
7468 preprocessing is triggered and parameterized.
7472 @item -gnatep=@var{file}
7473 @cindex @option{-gnatep} (@command{gcc})
7474 This switch indicates to the compiler the file name (without directory
7475 information) of the preprocessor data file to use. The preprocessor data file
7476 should be found in the source directories.
7479 A preprocessing data file is a text file with significant lines indicating
7480 how should be preprocessed either a specific source or all sources not
7481 mentioned in other lines. A significant line is a nonempty, non-comment line.
7482 Comments are similar to Ada comments.
7485 Each significant line starts with either a literal string or the character '*'.
7486 A literal string is the file name (without directory information) of the source
7487 to preprocess. A character '*' indicates the preprocessing for all the sources
7488 that are not specified explicitly on other lines (order of the lines is not
7489 significant). It is an error to have two lines with the same file name or two
7490 lines starting with the character '*'.
7493 After the file name or the character '*', another optional literal string
7494 indicating the file name of the definition file to be used for preprocessing
7495 (@pxref{Form of Definitions File}). The definition files are found by the
7496 compiler in one of the source directories. In some cases, when compiling
7497 a source in a directory other than the current directory, if the definition
7498 file is in the current directory, it may be necessary to add the current
7499 directory as a source directory through switch ^-I.^/SEARCH=[]^, otherwise
7500 the compiler would not find the definition file.
7503 Then, optionally, ^switches^switches^ similar to those of @code{gnatprep} may
7504 be found. Those ^switches^switches^ are:
7509 Causes both preprocessor lines and the lines deleted by
7510 preprocessing to be replaced by blank lines, preserving the line number.
7511 This ^switch^switch^ is always implied; however, if specified after @option{-c}
7512 it cancels the effect of @option{-c}.
7515 Causes both preprocessor lines and the lines deleted
7516 by preprocessing to be retained as comments marked
7517 with the special string ``@code{--! }''.
7519 @item -Dsymbol=value
7520 Define or redefine a symbol, associated with value. A symbol is an Ada
7521 identifier, or an Ada reserved word, with the exception of @code{if},
7522 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7523 @code{value} is either a literal string, an Ada identifier or any Ada reserved
7524 word. A symbol declared with this ^switch^switch^ replaces a symbol with the
7525 same name defined in a definition file.
7528 Causes a sorted list of symbol names and values to be
7529 listed on the standard output file.
7532 Causes undefined symbols to be treated as having the value @code{FALSE}
7534 of a preprocessor test. In the absence of this option, an undefined symbol in
7535 a @code{#if} or @code{#elsif} test will be treated as an error.
7540 Examples of valid lines in a preprocessor data file:
7543 "toto.adb" "prep.def" -u
7544 -- preprocess "toto.adb", using definition file "prep.def",
7545 -- undefined symbol are False.
7548 -- preprocess all other sources without a definition file;
7549 -- suppressed lined are commented; symbol VERSION has the value V101.
7551 "titi.adb" "prep2.def" -s
7552 -- preprocess "titi.adb", using definition file "prep2.def";
7553 -- list all symbols with their values.
7556 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=value@r{]}
7557 @cindex @option{-gnateD} (@command{gcc})
7558 Define or redefine a preprocessing symbol, associated with value. If no value
7559 is given on the command line, then the value of the symbol is @code{True}.
7560 A symbol is an identifier, following normal Ada (case-insensitive)
7561 rules for its syntax, and value is any sequence (including an empty sequence)
7562 of characters from the set (letters, digits, period, underline).
7563 Ada reserved words may be used as symbols, with the exceptions of @code{if},
7564 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7567 A symbol declared with this ^switch^switch^ on the command line replaces a
7568 symbol with the same name either in a definition file or specified with a
7569 ^switch^switch^ -D in the preprocessor data file.
7572 This switch is similar to switch @option{^-D^/ASSOCIATE^} of @code{gnatprep}.
7575 When integrated preprocessing is performed and the preprocessor modifies
7576 the source text, write the result of this preprocessing into a file
7577 <source>^.prep^_prep^.
7581 @node Code Generation Control
7582 @subsection Code Generation Control
7586 The GCC technology provides a wide range of target dependent
7587 @option{-m} switches for controlling
7588 details of code generation with respect to different versions of
7589 architectures. This includes variations in instruction sets (e.g.@:
7590 different members of the power pc family), and different requirements
7591 for optimal arrangement of instructions (e.g.@: different members of
7592 the x86 family). The list of available @option{-m} switches may be
7593 found in the GCC documentation.
7595 Use of these @option{-m} switches may in some cases result in improved
7598 The GNAT Pro technology is tested and qualified without any
7599 @option{-m} switches,
7600 so generally the most reliable approach is to avoid the use of these
7601 switches. However, we generally expect most of these switches to work
7602 successfully with GNAT Pro, and many customers have reported successful
7603 use of these options.
7605 Our general advice is to avoid the use of @option{-m} switches unless
7606 special needs lead to requirements in this area. In particular,
7607 there is no point in using @option{-m} switches to improve performance
7608 unless you actually see a performance improvement.
7612 @subsection Return Codes
7613 @cindex Return Codes
7614 @cindex @option{/RETURN_CODES=VMS}
7617 On VMS, GNAT compiled programs return POSIX-style codes by default,
7618 e.g.@: @option{/RETURN_CODES=POSIX}.
7620 To enable VMS style return codes, use GNAT BIND and LINK with the option
7621 @option{/RETURN_CODES=VMS}. For example:
7624 GNAT BIND MYMAIN.ALI /RETURN_CODES=VMS
7625 GNAT LINK MYMAIN.ALI /RETURN_CODES=VMS
7629 Programs built with /RETURN_CODES=VMS are suitable to be called in
7630 VMS DCL scripts. Programs compiled with the default /RETURN_CODES=POSIX
7631 are suitable for spawning with appropriate GNAT RTL routines.
7635 @node Search Paths and the Run-Time Library (RTL)
7636 @section Search Paths and the Run-Time Library (RTL)
7639 With the GNAT source-based library system, the compiler must be able to
7640 find source files for units that are needed by the unit being compiled.
7641 Search paths are used to guide this process.
7643 The compiler compiles one source file whose name must be given
7644 explicitly on the command line. In other words, no searching is done
7645 for this file. To find all other source files that are needed (the most
7646 common being the specs of units), the compiler examines the following
7647 directories, in the following order:
7651 The directory containing the source file of the main unit being compiled
7652 (the file name on the command line).
7655 Each directory named by an @option{^-I^/SOURCE_SEARCH^} switch given on the
7656 @command{gcc} command line, in the order given.
7659 @findex ADA_PRJ_INCLUDE_FILE
7660 Each of the directories listed in the text file whose name is given
7661 by the @env{ADA_PRJ_INCLUDE_FILE} ^environment variable^logical name^.
7664 @env{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
7665 driver when project files are used. It should not normally be set
7669 @findex ADA_INCLUDE_PATH
7670 Each of the directories listed in the value of the
7671 @env{ADA_INCLUDE_PATH} ^environment variable^logical name^.
7673 Construct this value
7674 exactly as the @env{PATH} environment variable: a list of directory
7675 names separated by colons (semicolons when working with the NT version).
7678 Normally, define this value as a logical name containing a comma separated
7679 list of directory names.
7681 This variable can also be defined by means of an environment string
7682 (an argument to the HP C exec* set of functions).
7686 DEFINE ANOTHER_PATH FOO:[BAG]
7687 DEFINE ADA_INCLUDE_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
7690 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
7691 first, followed by the standard Ada
7692 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADAINCLUDE].
7693 If this is not redefined, the user will obtain the HP Ada 83 IO packages
7694 (Text_IO, Sequential_IO, etc)
7695 instead of the standard Ada packages. Thus, in order to get the standard Ada
7696 packages by default, ADA_INCLUDE_PATH must be redefined.
7700 The content of the @file{ada_source_path} file which is part of the GNAT
7701 installation tree and is used to store standard libraries such as the
7702 GNAT Run Time Library (RTL) source files.
7704 @ref{Installing a library}
7709 Specifying the switch @option{^-I-^/NOCURRENT_DIRECTORY^}
7710 inhibits the use of the directory
7711 containing the source file named in the command line. You can still
7712 have this directory on your search path, but in this case it must be
7713 explicitly requested with a @option{^-I^/SOURCE_SEARCH^} switch.
7715 Specifying the switch @option{-nostdinc}
7716 inhibits the search of the default location for the GNAT Run Time
7717 Library (RTL) source files.
7719 The compiler outputs its object files and ALI files in the current
7722 Caution: The object file can be redirected with the @option{-o} switch;
7723 however, @command{gcc} and @code{gnat1} have not been coordinated on this
7724 so the @file{ALI} file will not go to the right place. Therefore, you should
7725 avoid using the @option{-o} switch.
7729 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
7730 children make up the GNAT RTL, together with the simple @code{System.IO}
7731 package used in the @code{"Hello World"} example. The sources for these units
7732 are needed by the compiler and are kept together in one directory. Not
7733 all of the bodies are needed, but all of the sources are kept together
7734 anyway. In a normal installation, you need not specify these directory
7735 names when compiling or binding. Either the environment variables or
7736 the built-in defaults cause these files to be found.
7738 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
7739 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
7740 consisting of child units of @code{GNAT}. This is a collection of generally
7741 useful types, subprograms, etc. @xref{Top, GNAT Reference Manual, About
7742 This Guid, gnat_rm, GNAT Reference Manual}, for further details.
7744 Besides simplifying access to the RTL, a major use of search paths is
7745 in compiling sources from multiple directories. This can make
7746 development environments much more flexible.
7748 @node Order of Compilation Issues
7749 @section Order of Compilation Issues
7752 If, in our earlier example, there was a spec for the @code{hello}
7753 procedure, it would be contained in the file @file{hello.ads}; yet this
7754 file would not have to be explicitly compiled. This is the result of the
7755 model we chose to implement library management. Some of the consequences
7756 of this model are as follows:
7760 There is no point in compiling specs (except for package
7761 specs with no bodies) because these are compiled as needed by clients. If
7762 you attempt a useless compilation, you will receive an error message.
7763 It is also useless to compile subunits because they are compiled as needed
7767 There are no order of compilation requirements: performing a
7768 compilation never obsoletes anything. The only way you can obsolete
7769 something and require recompilations is to modify one of the
7770 source files on which it depends.
7773 There is no library as such, apart from the ALI files
7774 (@pxref{The Ada Library Information Files}, for information on the format
7775 of these files). For now we find it convenient to create separate ALI files,
7776 but eventually the information therein may be incorporated into the object
7780 When you compile a unit, the source files for the specs of all units
7781 that it @code{with}'s, all its subunits, and the bodies of any generics it
7782 instantiates must be available (reachable by the search-paths mechanism
7783 described above), or you will receive a fatal error message.
7790 The following are some typical Ada compilation command line examples:
7793 @item $ gcc -c xyz.adb
7794 Compile body in file @file{xyz.adb} with all default options.
7797 @item $ gcc -c -O2 -gnata xyz-def.adb
7800 @item $ GNAT COMPILE /OPTIMIZE=ALL -gnata xyz-def.adb
7803 Compile the child unit package in file @file{xyz-def.adb} with extensive
7804 optimizations, and pragma @code{Assert}/@code{Debug} statements
7807 @item $ gcc -c -gnatc abc-def.adb
7808 Compile the subunit in file @file{abc-def.adb} in semantic-checking-only
7812 @node Binding Using gnatbind
7813 @chapter Binding Using @code{gnatbind}
7817 * Running gnatbind::
7818 * Switches for gnatbind::
7819 * Command-Line Access::
7820 * Search Paths for gnatbind::
7821 * Examples of gnatbind Usage::
7825 This chapter describes the GNAT binder, @code{gnatbind}, which is used
7826 to bind compiled GNAT objects.
7828 Note: to invoke @code{gnatbind} with a project file, use the @code{gnat}
7829 driver (see @ref{The GNAT Driver and Project Files}).
7831 The @code{gnatbind} program performs four separate functions:
7835 Checks that a program is consistent, in accordance with the rules in
7836 Chapter 10 of the Ada Reference Manual. In particular, error
7837 messages are generated if a program uses inconsistent versions of a
7841 Checks that an acceptable order of elaboration exists for the program
7842 and issues an error message if it cannot find an order of elaboration
7843 that satisfies the rules in Chapter 10 of the Ada Language Manual.
7846 Generates a main program incorporating the given elaboration order.
7847 This program is a small Ada package (body and spec) that
7848 must be subsequently compiled
7849 using the GNAT compiler. The necessary compilation step is usually
7850 performed automatically by @command{gnatlink}. The two most important
7851 functions of this program
7852 are to call the elaboration routines of units in an appropriate order
7853 and to call the main program.
7856 Determines the set of object files required by the given main program.
7857 This information is output in the forms of comments in the generated program,
7858 to be read by the @command{gnatlink} utility used to link the Ada application.
7861 @node Running gnatbind
7862 @section Running @code{gnatbind}
7865 The form of the @code{gnatbind} command is
7868 $ gnatbind @ovar{switches} @var{mainprog}@r{[}.ali@r{]} @ovar{switches}
7872 where @file{@var{mainprog}.adb} is the Ada file containing the main program
7873 unit body. If no switches are specified, @code{gnatbind} constructs an Ada
7874 package in two files whose names are
7875 @file{b~@var{mainprog}.ads}, and @file{b~@var{mainprog}.adb}.
7876 For example, if given the
7877 parameter @file{hello.ali}, for a main program contained in file
7878 @file{hello.adb}, the binder output files would be @file{b~hello.ads}
7879 and @file{b~hello.adb}.
7881 When doing consistency checking, the binder takes into consideration
7882 any source files it can locate. For example, if the binder determines
7883 that the given main program requires the package @code{Pack}, whose
7885 file is @file{pack.ali} and whose corresponding source spec file is
7886 @file{pack.ads}, it attempts to locate the source file @file{pack.ads}
7887 (using the same search path conventions as previously described for the
7888 @command{gcc} command). If it can locate this source file, it checks that
7890 or source checksums of the source and its references to in @file{ALI} files
7891 match. In other words, any @file{ALI} files that mentions this spec must have
7892 resulted from compiling this version of the source file (or in the case
7893 where the source checksums match, a version close enough that the
7894 difference does not matter).
7896 @cindex Source files, use by binder
7897 The effect of this consistency checking, which includes source files, is
7898 that the binder ensures that the program is consistent with the latest
7899 version of the source files that can be located at bind time. Editing a
7900 source file without compiling files that depend on the source file cause
7901 error messages to be generated by the binder.
7903 For example, suppose you have a main program @file{hello.adb} and a
7904 package @code{P}, from file @file{p.ads} and you perform the following
7909 Enter @code{gcc -c hello.adb} to compile the main program.
7912 Enter @code{gcc -c p.ads} to compile package @code{P}.
7915 Edit file @file{p.ads}.
7918 Enter @code{gnatbind hello}.
7922 At this point, the file @file{p.ali} contains an out-of-date time stamp
7923 because the file @file{p.ads} has been edited. The attempt at binding
7924 fails, and the binder generates the following error messages:
7927 error: "hello.adb" must be recompiled ("p.ads" has been modified)
7928 error: "p.ads" has been modified and must be recompiled
7932 Now both files must be recompiled as indicated, and then the bind can
7933 succeed, generating a main program. You need not normally be concerned
7934 with the contents of this file, but for reference purposes a sample
7935 binder output file is given in @ref{Example of Binder Output File}.
7937 In most normal usage, the default mode of @command{gnatbind} which is to
7938 generate the main package in Ada, as described in the previous section.
7939 In particular, this means that any Ada programmer can read and understand
7940 the generated main program. It can also be debugged just like any other
7941 Ada code provided the @option{^-g^/DEBUG^} switch is used for
7942 @command{gnatbind} and @command{gnatlink}.
7944 However for some purposes it may be convenient to generate the main
7945 program in C rather than Ada. This may for example be helpful when you
7946 are generating a mixed language program with the main program in C. The
7947 GNAT compiler itself is an example.
7948 The use of the @option{^-C^/BIND_FILE=C^} switch
7949 for both @code{gnatbind} and @command{gnatlink} will cause the program to
7950 be generated in C (and compiled using the gnu C compiler).
7952 @node Switches for gnatbind
7953 @section Switches for @command{gnatbind}
7956 The following switches are available with @code{gnatbind}; details will
7957 be presented in subsequent sections.
7960 * Consistency-Checking Modes::
7961 * Binder Error Message Control::
7962 * Elaboration Control::
7964 * Binding with Non-Ada Main Programs::
7965 * Binding Programs with No Main Subprogram::
7972 @cindex @option{--version} @command{gnatbind}
7973 Display Copyright and version, then exit disregarding all other options.
7976 @cindex @option{--help} @command{gnatbind}
7977 If @option{--version} was not used, display usage, then exit disregarding
7981 @cindex @option{-a} @command{gnatbind}
7982 Indicates that, if supported by the platform, the adainit procedure should
7983 be treated as an initialisation routine by the linker (a constructor). This
7984 is intended to be used by the Project Manager to automatically initialize
7985 shared Stand-Alone Libraries.
7987 @item ^-aO^/OBJECT_SEARCH^
7988 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatbind})
7989 Specify directory to be searched for ALI files.
7991 @item ^-aI^/SOURCE_SEARCH^
7992 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
7993 Specify directory to be searched for source file.
7995 @item ^-A^/BIND_FILE=ADA^
7996 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatbind})
7997 Generate binder program in Ada (default)
7999 @item ^-b^/REPORT_ERRORS=BRIEF^
8000 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@command{gnatbind})
8001 Generate brief messages to @file{stderr} even if verbose mode set.
8003 @item ^-c^/NOOUTPUT^
8004 @cindex @option{^-c^/NOOUTPUT^} (@command{gnatbind})
8005 Check only, no generation of binder output file.
8007 @item ^-C^/BIND_FILE=C^
8008 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatbind})
8009 Generate binder program in C
8011 @item ^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
8012 @cindex @option{^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}} (@command{gnatbind})
8013 This switch can be used to change the default task stack size value
8014 to a specified size @var{nn}, which is expressed in bytes by default, or
8015 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
8017 In the absence of a @samp{@r{[}k@r{|}m@r{]}} suffix, this switch is equivalent,
8018 in effect, to completing all task specs with
8019 @smallexample @c ada
8020 pragma Storage_Size (nn);
8022 When they do not already have such a pragma.
8024 @item ^-D^/DEFAULT_SECONDARY_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
8025 @cindex @option{^-D^/DEFAULT_SECONDARY_STACK_SIZE=nnnnn^} (@command{gnatbind})
8026 This switch can be used to change the default secondary stack size value
8027 to a specified size @var{nn}, which is expressed in bytes by default, or
8028 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
8031 The secondary stack is used to deal with functions that return a variable
8032 sized result, for example a function returning an unconstrained
8033 String. There are two ways in which this secondary stack is allocated.
8035 For most targets, the secondary stack is growing on demand and is allocated
8036 as a chain of blocks in the heap. The -D option is not very
8037 relevant. It only give some control over the size of the allocated
8038 blocks (whose size is the minimum of the default secondary stack size value,
8039 and the actual size needed for the current allocation request).
8041 For certain targets, notably VxWorks 653,
8042 the secondary stack is allocated by carving off a fixed ratio chunk of the
8043 primary task stack. The -D option is used to define the
8044 size of the environment task's secondary stack.
8046 @item ^-e^/ELABORATION_DEPENDENCIES^
8047 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@command{gnatbind})
8048 Output complete list of elaboration-order dependencies.
8050 @item ^-E^/STORE_TRACEBACKS^
8051 @cindex @option{^-E^/STORE_TRACEBACKS^} (@command{gnatbind})
8052 Store tracebacks in exception occurrences when the target supports it.
8053 This is the default with the zero cost exception mechanism.
8055 @c The following may get moved to an appendix
8056 This option is currently supported on the following targets:
8057 all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks.
8059 See also the packages @code{GNAT.Traceback} and
8060 @code{GNAT.Traceback.Symbolic} for more information.
8062 Note that on x86 ports, you must not use @option{-fomit-frame-pointer}
8063 @command{gcc} option.
8066 @item ^-F^/FORCE_ELABS_FLAGS^
8067 @cindex @option{^-F^/FORCE_ELABS_FLAGS^} (@command{gnatbind})
8068 Force the checks of elaboration flags. @command{gnatbind} does not normally
8069 generate checks of elaboration flags for the main executable, except when
8070 a Stand-Alone Library is used. However, there are cases when this cannot be
8071 detected by gnatbind. An example is importing an interface of a Stand-Alone
8072 Library through a pragma Import and only specifying through a linker switch
8073 this Stand-Alone Library. This switch is used to guarantee that elaboration
8074 flag checks are generated.
8077 @cindex @option{^-h^/HELP^} (@command{gnatbind})
8078 Output usage (help) information
8081 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8082 Specify directory to be searched for source and ALI files.
8084 @item ^-I-^/NOCURRENT_DIRECTORY^
8085 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatbind})
8086 Do not look for sources in the current directory where @code{gnatbind} was
8087 invoked, and do not look for ALI files in the directory containing the
8088 ALI file named in the @code{gnatbind} command line.
8090 @item ^-l^/ORDER_OF_ELABORATION^
8091 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@command{gnatbind})
8092 Output chosen elaboration order.
8094 @item ^-L@var{xxx}^/BUILD_LIBRARY=@var{xxx}^
8095 @cindex @option{^-L^/BUILD_LIBRARY^} (@command{gnatbind})
8096 Bind the units for library building. In this case the adainit and
8097 adafinal procedures (@pxref{Binding with Non-Ada Main Programs})
8098 are renamed to ^@var{xxx}init^@var{XXX}INIT^ and
8099 ^@var{xxx}final^@var{XXX}FINAL^.
8100 Implies ^-n^/NOCOMPILE^.
8102 (@xref{GNAT and Libraries}, for more details.)
8105 On OpenVMS, these init and final procedures are exported in uppercase
8106 letters. For example if /BUILD_LIBRARY=toto is used, the exported name of
8107 the init procedure will be "TOTOINIT" and the exported name of the final
8108 procedure will be "TOTOFINAL".
8111 @item ^-Mxyz^/RENAME_MAIN=xyz^
8112 @cindex @option{^-M^/RENAME_MAIN^} (@command{gnatbind})
8113 Rename generated main program from main to xyz. This option is
8114 supported on cross environments only.
8116 @item ^-m^/ERROR_LIMIT=^@var{n}
8117 @cindex @option{^-m^/ERROR_LIMIT^} (@command{gnatbind})
8118 Limit number of detected errors or warnings to @var{n}, where @var{n} is
8119 in the range 1..999999. The default value if no switch is
8120 given is 9999. If the number of warnings reaches this limit, then a
8121 message is output and further warnings are suppressed, the bind
8122 continues in this case. If the number of errors reaches this
8123 limit, then a message is output and the bind is abandoned.
8124 A value of zero means that no limit is enforced. The equal
8128 Furthermore, under Windows, the sources pointed to by the libraries path
8129 set in the registry are not searched for.
8133 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8137 @cindex @option{-nostdinc} (@command{gnatbind})
8138 Do not look for sources in the system default directory.
8141 @cindex @option{-nostdlib} (@command{gnatbind})
8142 Do not look for library files in the system default directory.
8144 @item --RTS=@var{rts-path}
8145 @cindex @option{--RTS} (@code{gnatbind})
8146 Specifies the default location of the runtime library. Same meaning as the
8147 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
8149 @item ^-o ^/OUTPUT=^@var{file}
8150 @cindex @option{^-o ^/OUTPUT^} (@command{gnatbind})
8151 Name the output file @var{file} (default is @file{b~@var{xxx}.adb}).
8152 Note that if this option is used, then linking must be done manually,
8153 gnatlink cannot be used.
8155 @item ^-O^/OBJECT_LIST^
8156 @cindex @option{^-O^/OBJECT_LIST^} (@command{gnatbind})
8159 @item ^-p^/PESSIMISTIC_ELABORATION^
8160 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@command{gnatbind})
8161 Pessimistic (worst-case) elaboration order
8164 @cindex @option{^-R^-R^} (@command{gnatbind})
8165 Output closure source list.
8167 @item ^-s^/READ_SOURCES=ALL^
8168 @cindex @option{^-s^/READ_SOURCES=ALL^} (@command{gnatbind})
8169 Require all source files to be present.
8171 @item ^-S@var{xxx}^/INITIALIZE_SCALARS=@var{xxx}^
8172 @cindex @option{^-S^/INITIALIZE_SCALARS^} (@command{gnatbind})
8173 Specifies the value to be used when detecting uninitialized scalar
8174 objects with pragma Initialize_Scalars.
8175 The @var{xxx} ^string specified with the switch^option^ may be either
8177 @item ``@option{^in^INVALID^}'' requesting an invalid value where possible
8178 @item ``@option{^lo^LOW^}'' for the lowest possible value
8179 @item ``@option{^hi^HIGH^}'' for the highest possible value
8180 @item ``@option{@var{xx}}'' for a value consisting of repeated bytes with the
8181 value @code{16#@var{xx}#} (i.e., @var{xx} is a string of two hexadecimal digits).
8184 In addition, you can specify @option{-Sev} to indicate that the value is
8185 to be set at run time. In this case, the program will look for an environment
8186 @cindex GNAT_INIT_SCALARS
8187 variable of the form @env{GNAT_INIT_SCALARS=@var{xx}}, where @var{xx} is one
8188 of @option{in/lo/hi/@var{xx}} with the same meanings as above.
8189 If no environment variable is found, or if it does not have a valid value,
8190 then the default is @option{in} (invalid values).
8194 @cindex @option{-static} (@code{gnatbind})
8195 Link against a static GNAT run time.
8198 @cindex @option{-shared} (@code{gnatbind})
8199 Link against a shared GNAT run time when available.
8202 @item ^-t^/NOTIME_STAMP_CHECK^
8203 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8204 Tolerate time stamp and other consistency errors
8206 @item ^-T@var{n}^/TIME_SLICE=@var{n}^
8207 @cindex @option{^-T^/TIME_SLICE^} (@code{gnatbind})
8208 Set the time slice value to @var{n} milliseconds. If the system supports
8209 the specification of a specific time slice value, then the indicated value
8210 is used. If the system does not support specific time slice values, but
8211 does support some general notion of round-robin scheduling, then any
8212 nonzero value will activate round-robin scheduling.
8214 A value of zero is treated specially. It turns off time
8215 slicing, and in addition, indicates to the tasking run time that the
8216 semantics should match as closely as possible the Annex D
8217 requirements of the Ada RM, and in particular sets the default
8218 scheduling policy to @code{FIFO_Within_Priorities}.
8220 @item ^-u@var{n}^/DYNAMIC_STACK_USAGE=@var{n}^
8221 @cindex @option{^-u^/DYNAMIC_STACK_USAGE^} (@code{gnatbind})
8222 Enable dynamic stack usage, with @var{n} results stored and displayed
8223 at program termination. A result is generated when a task
8224 terminates. Results that can't be stored are displayed on the fly, at
8225 task termination. This option is currently not supported on Itanium
8226 platforms. (See @ref{Dynamic Stack Usage Analysis} for details.)
8228 @item ^-v^/REPORT_ERRORS=VERBOSE^
8229 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8230 Verbose mode. Write error messages, header, summary output to
8235 @cindex @option{-w} (@code{gnatbind})
8236 Warning mode (@var{x}=s/e for suppress/treat as error)
8240 @item /WARNINGS=NORMAL
8241 @cindex @option{/WARNINGS} (@code{gnatbind})
8242 Normal warnings mode. Warnings are issued but ignored
8244 @item /WARNINGS=SUPPRESS
8245 @cindex @option{/WARNINGS} (@code{gnatbind})
8246 All warning messages are suppressed
8248 @item /WARNINGS=ERROR
8249 @cindex @option{/WARNINGS} (@code{gnatbind})
8250 Warning messages are treated as fatal errors
8253 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8254 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8255 Override default wide character encoding for standard Text_IO files.
8257 @item ^-x^/READ_SOURCES=NONE^
8258 @cindex @option{^-x^/READ_SOURCES^} (@code{gnatbind})
8259 Exclude source files (check object consistency only).
8262 @item /READ_SOURCES=AVAILABLE
8263 @cindex @option{/READ_SOURCES} (@code{gnatbind})
8264 Default mode, in which sources are checked for consistency only if
8268 @item ^-y^/ENABLE_LEAP_SECONDS^
8269 @cindex @option{^-y^/ENABLE_LEAP_SECONDS^} (@code{gnatbind})
8270 Enable leap seconds support in @code{Ada.Calendar} and its children.
8272 @item ^-z^/ZERO_MAIN^
8273 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8279 You may obtain this listing of switches by running @code{gnatbind} with
8283 @node Consistency-Checking Modes
8284 @subsection Consistency-Checking Modes
8287 As described earlier, by default @code{gnatbind} checks
8288 that object files are consistent with one another and are consistent
8289 with any source files it can locate. The following switches control binder
8294 @item ^-s^/READ_SOURCES=ALL^
8295 @cindex @option{^-s^/READ_SOURCES=ALL^} (@code{gnatbind})
8296 Require source files to be present. In this mode, the binder must be
8297 able to locate all source files that are referenced, in order to check
8298 their consistency. In normal mode, if a source file cannot be located it
8299 is simply ignored. If you specify this switch, a missing source
8302 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8303 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8304 Override default wide character encoding for standard Text_IO files.
8305 Normally the default wide character encoding method used for standard
8306 [Wide_[Wide_]]Text_IO files is taken from the encoding specified for
8307 the main source input (see description of switch
8308 @option{^-gnatWx^/WIDE_CHARACTER_ENCODING^} for the compiler). The
8309 use of this switch for the binder (which has the same set of
8310 possible arguments) overrides this default as specified.
8312 @item ^-x^/READ_SOURCES=NONE^
8313 @cindex @option{^-x^/READ_SOURCES=NONE^} (@code{gnatbind})
8314 Exclude source files. In this mode, the binder only checks that ALI
8315 files are consistent with one another. Source files are not accessed.
8316 The binder runs faster in this mode, and there is still a guarantee that
8317 the resulting program is self-consistent.
8318 If a source file has been edited since it was last compiled, and you
8319 specify this switch, the binder will not detect that the object
8320 file is out of date with respect to the source file. Note that this is the
8321 mode that is automatically used by @command{gnatmake} because in this
8322 case the checking against sources has already been performed by
8323 @command{gnatmake} in the course of compilation (i.e.@: before binding).
8326 @item /READ_SOURCES=AVAILABLE
8327 @cindex @code{/READ_SOURCES=AVAILABLE} (@code{gnatbind})
8328 This is the default mode in which source files are checked if they are
8329 available, and ignored if they are not available.
8333 @node Binder Error Message Control
8334 @subsection Binder Error Message Control
8337 The following switches provide control over the generation of error
8338 messages from the binder:
8342 @item ^-v^/REPORT_ERRORS=VERBOSE^
8343 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8344 Verbose mode. In the normal mode, brief error messages are generated to
8345 @file{stderr}. If this switch is present, a header is written
8346 to @file{stdout} and any error messages are directed to @file{stdout}.
8347 All that is written to @file{stderr} is a brief summary message.
8349 @item ^-b^/REPORT_ERRORS=BRIEF^
8350 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@code{gnatbind})
8351 Generate brief error messages to @file{stderr} even if verbose mode is
8352 specified. This is relevant only when used with the
8353 @option{^-v^/REPORT_ERRORS=VERBOSE^} switch.
8357 @cindex @option{-m} (@code{gnatbind})
8358 Limits the number of error messages to @var{n}, a decimal integer in the
8359 range 1-999. The binder terminates immediately if this limit is reached.
8362 @cindex @option{-M} (@code{gnatbind})
8363 Renames the generated main program from @code{main} to @code{xxx}.
8364 This is useful in the case of some cross-building environments, where
8365 the actual main program is separate from the one generated
8369 @item ^-ws^/WARNINGS=SUPPRESS^
8370 @cindex @option{^-ws^/WARNINGS=SUPPRESS^} (@code{gnatbind})
8372 Suppress all warning messages.
8374 @item ^-we^/WARNINGS=ERROR^
8375 @cindex @option{^-we^/WARNINGS=ERROR^} (@code{gnatbind})
8376 Treat any warning messages as fatal errors.
8379 @item /WARNINGS=NORMAL
8380 Standard mode with warnings generated, but warnings do not get treated
8384 @item ^-t^/NOTIME_STAMP_CHECK^
8385 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8386 @cindex Time stamp checks, in binder
8387 @cindex Binder consistency checks
8388 @cindex Consistency checks, in binder
8389 The binder performs a number of consistency checks including:
8393 Check that time stamps of a given source unit are consistent
8395 Check that checksums of a given source unit are consistent
8397 Check that consistent versions of @code{GNAT} were used for compilation
8399 Check consistency of configuration pragmas as required
8403 Normally failure of such checks, in accordance with the consistency
8404 requirements of the Ada Reference Manual, causes error messages to be
8405 generated which abort the binder and prevent the output of a binder
8406 file and subsequent link to obtain an executable.
8408 The @option{^-t^/NOTIME_STAMP_CHECK^} switch converts these error messages
8409 into warnings, so that
8410 binding and linking can continue to completion even in the presence of such
8411 errors. The result may be a failed link (due to missing symbols), or a
8412 non-functional executable which has undefined semantics.
8413 @emph{This means that
8414 @option{^-t^/NOTIME_STAMP_CHECK^} should be used only in unusual situations,
8418 @node Elaboration Control
8419 @subsection Elaboration Control
8422 The following switches provide additional control over the elaboration
8423 order. For full details see @ref{Elaboration Order Handling in GNAT}.
8426 @item ^-p^/PESSIMISTIC_ELABORATION^
8427 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@code{gnatbind})
8428 Normally the binder attempts to choose an elaboration order that is
8429 likely to minimize the likelihood of an elaboration order error resulting
8430 in raising a @code{Program_Error} exception. This switch reverses the
8431 action of the binder, and requests that it deliberately choose an order
8432 that is likely to maximize the likelihood of an elaboration error.
8433 This is useful in ensuring portability and avoiding dependence on
8434 accidental fortuitous elaboration ordering.
8436 Normally it only makes sense to use the @option{^-p^/PESSIMISTIC_ELABORATION^}
8438 elaboration checking is used (@option{-gnatE} switch used for compilation).
8439 This is because in the default static elaboration mode, all necessary
8440 @code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted.
8441 These implicit pragmas are still respected by the binder in
8442 @option{^-p^/PESSIMISTIC_ELABORATION^} mode, so a
8443 safe elaboration order is assured.
8446 @node Output Control
8447 @subsection Output Control
8450 The following switches allow additional control over the output
8451 generated by the binder.
8456 @item ^-A^/BIND_FILE=ADA^
8457 @cindex @option{^-A^/BIND_FILE=ADA^} (@code{gnatbind})
8458 Generate binder program in Ada (default). The binder program is named
8459 @file{b~@var{mainprog}.adb} by default. This can be changed with
8460 @option{^-o^/OUTPUT^} @code{gnatbind} option.
8462 @item ^-c^/NOOUTPUT^
8463 @cindex @option{^-c^/NOOUTPUT^} (@code{gnatbind})
8464 Check only. Do not generate the binder output file. In this mode the
8465 binder performs all error checks but does not generate an output file.
8467 @item ^-C^/BIND_FILE=C^
8468 @cindex @option{^-C^/BIND_FILE=C^} (@code{gnatbind})
8469 Generate binder program in C. The binder program is named
8470 @file{b_@var{mainprog}.c}.
8471 This can be changed with @option{^-o^/OUTPUT^} @code{gnatbind}
8474 @item ^-e^/ELABORATION_DEPENDENCIES^
8475 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@code{gnatbind})
8476 Output complete list of elaboration-order dependencies, showing the
8477 reason for each dependency. This output can be rather extensive but may
8478 be useful in diagnosing problems with elaboration order. The output is
8479 written to @file{stdout}.
8482 @cindex @option{^-h^/HELP^} (@code{gnatbind})
8483 Output usage information. The output is written to @file{stdout}.
8485 @item ^-K^/LINKER_OPTION_LIST^
8486 @cindex @option{^-K^/LINKER_OPTION_LIST^} (@code{gnatbind})
8487 Output linker options to @file{stdout}. Includes library search paths,
8488 contents of pragmas Ident and Linker_Options, and libraries added
8491 @item ^-l^/ORDER_OF_ELABORATION^
8492 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@code{gnatbind})
8493 Output chosen elaboration order. The output is written to @file{stdout}.
8495 @item ^-O^/OBJECT_LIST^
8496 @cindex @option{^-O^/OBJECT_LIST^} (@code{gnatbind})
8497 Output full names of all the object files that must be linked to provide
8498 the Ada component of the program. The output is written to @file{stdout}.
8499 This list includes the files explicitly supplied and referenced by the user
8500 as well as implicitly referenced run-time unit files. The latter are
8501 omitted if the corresponding units reside in shared libraries. The
8502 directory names for the run-time units depend on the system configuration.
8504 @item ^-o ^/OUTPUT=^@var{file}
8505 @cindex @option{^-o^/OUTPUT^} (@code{gnatbind})
8506 Set name of output file to @var{file} instead of the normal
8507 @file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada
8508 binder generated body filename. In C mode you would normally give
8509 @var{file} an extension of @file{.c} because it will be a C source program.
8510 Note that if this option is used, then linking must be done manually.
8511 It is not possible to use gnatlink in this case, since it cannot locate
8514 @item ^-r^/RESTRICTION_LIST^
8515 @cindex @option{^-r^/RESTRICTION_LIST^} (@code{gnatbind})
8516 Generate list of @code{pragma Restrictions} that could be applied to
8517 the current unit. This is useful for code audit purposes, and also may
8518 be used to improve code generation in some cases.
8522 @node Binding with Non-Ada Main Programs
8523 @subsection Binding with Non-Ada Main Programs
8526 In our description so far we have assumed that the main
8527 program is in Ada, and that the task of the binder is to generate a
8528 corresponding function @code{main} that invokes this Ada main
8529 program. GNAT also supports the building of executable programs where
8530 the main program is not in Ada, but some of the called routines are
8531 written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}).
8532 The following switch is used in this situation:
8536 @cindex @option{^-n^/NOMAIN^} (@code{gnatbind})
8537 No main program. The main program is not in Ada.
8541 In this case, most of the functions of the binder are still required,
8542 but instead of generating a main program, the binder generates a file
8543 containing the following callable routines:
8548 You must call this routine to initialize the Ada part of the program by
8549 calling the necessary elaboration routines. A call to @code{adainit} is
8550 required before the first call to an Ada subprogram.
8552 Note that it is assumed that the basic execution environment must be setup
8553 to be appropriate for Ada execution at the point where the first Ada
8554 subprogram is called. In particular, if the Ada code will do any
8555 floating-point operations, then the FPU must be setup in an appropriate
8556 manner. For the case of the x86, for example, full precision mode is
8557 required. The procedure GNAT.Float_Control.Reset may be used to ensure
8558 that the FPU is in the right state.
8562 You must call this routine to perform any library-level finalization
8563 required by the Ada subprograms. A call to @code{adafinal} is required
8564 after the last call to an Ada subprogram, and before the program
8569 If the @option{^-n^/NOMAIN^} switch
8570 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8571 @cindex Binder, multiple input files
8572 is given, more than one ALI file may appear on
8573 the command line for @code{gnatbind}. The normal @dfn{closure}
8574 calculation is performed for each of the specified units. Calculating
8575 the closure means finding out the set of units involved by tracing
8576 @code{with} references. The reason it is necessary to be able to
8577 specify more than one ALI file is that a given program may invoke two or
8578 more quite separate groups of Ada units.
8580 The binder takes the name of its output file from the last specified ALI
8581 file, unless overridden by the use of the @option{^-o file^/OUTPUT=file^}.
8582 @cindex @option{^-o^/OUTPUT^} (@command{gnatbind})
8583 The output is an Ada unit in source form that can
8584 be compiled with GNAT unless the -C switch is used in which case the
8585 output is a C source file, which must be compiled using the C compiler.
8586 This compilation occurs automatically as part of the @command{gnatlink}
8589 Currently the GNAT run time requires a FPU using 80 bits mode
8590 precision. Under targets where this is not the default it is required to
8591 call GNAT.Float_Control.Reset before using floating point numbers (this
8592 include float computation, float input and output) in the Ada code. A
8593 side effect is that this could be the wrong mode for the foreign code
8594 where floating point computation could be broken after this call.
8596 @node Binding Programs with No Main Subprogram
8597 @subsection Binding Programs with No Main Subprogram
8600 It is possible to have an Ada program which does not have a main
8601 subprogram. This program will call the elaboration routines of all the
8602 packages, then the finalization routines.
8604 The following switch is used to bind programs organized in this manner:
8607 @item ^-z^/ZERO_MAIN^
8608 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8609 Normally the binder checks that the unit name given on the command line
8610 corresponds to a suitable main subprogram. When this switch is used,
8611 a list of ALI files can be given, and the execution of the program
8612 consists of elaboration of these units in an appropriate order. Note
8613 that the default wide character encoding method for standard Text_IO
8614 files is always set to Brackets if this switch is set (you can use
8616 @option{^-Wx^WIDE_CHARACTER_ENCODING^} to override this default).
8619 @node Command-Line Access
8620 @section Command-Line Access
8623 The package @code{Ada.Command_Line} provides access to the command-line
8624 arguments and program name. In order for this interface to operate
8625 correctly, the two variables
8637 are declared in one of the GNAT library routines. These variables must
8638 be set from the actual @code{argc} and @code{argv} values passed to the
8639 main program. With no @option{^n^/NOMAIN^} present, @code{gnatbind}
8640 generates the C main program to automatically set these variables.
8641 If the @option{^n^/NOMAIN^} switch is used, there is no automatic way to
8642 set these variables. If they are not set, the procedures in
8643 @code{Ada.Command_Line} will not be available, and any attempt to use
8644 them will raise @code{Constraint_Error}. If command line access is
8645 required, your main program must set @code{gnat_argc} and
8646 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
8649 @node Search Paths for gnatbind
8650 @section Search Paths for @code{gnatbind}
8653 The binder takes the name of an ALI file as its argument and needs to
8654 locate source files as well as other ALI files to verify object consistency.
8656 For source files, it follows exactly the same search rules as @command{gcc}
8657 (@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the
8658 directories searched are:
8662 The directory containing the ALI file named in the command line, unless
8663 the switch @option{^-I-^/NOCURRENT_DIRECTORY^} is specified.
8666 All directories specified by @option{^-I^/SEARCH^}
8667 switches on the @code{gnatbind}
8668 command line, in the order given.
8671 @findex ADA_PRJ_OBJECTS_FILE
8672 Each of the directories listed in the text file whose name is given
8673 by the @env{ADA_PRJ_OBJECTS_FILE} ^environment variable^logical name^.
8676 @env{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
8677 driver when project files are used. It should not normally be set
8681 @findex ADA_OBJECTS_PATH
8682 Each of the directories listed in the value of the
8683 @env{ADA_OBJECTS_PATH} ^environment variable^logical name^.
8685 Construct this value
8686 exactly as the @env{PATH} environment variable: a list of directory
8687 names separated by colons (semicolons when working with the NT version
8691 Normally, define this value as a logical name containing a comma separated
8692 list of directory names.
8694 This variable can also be defined by means of an environment string
8695 (an argument to the HP C exec* set of functions).
8699 DEFINE ANOTHER_PATH FOO:[BAG]
8700 DEFINE ADA_OBJECTS_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
8703 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
8704 first, followed by the standard Ada
8705 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB].
8706 If this is not redefined, the user will obtain the HP Ada 83 IO packages
8707 (Text_IO, Sequential_IO, etc)
8708 instead of the standard Ada packages. Thus, in order to get the standard Ada
8709 packages by default, ADA_OBJECTS_PATH must be redefined.
8713 The content of the @file{ada_object_path} file which is part of the GNAT
8714 installation tree and is used to store standard libraries such as the
8715 GNAT Run Time Library (RTL) unless the switch @option{-nostdlib} is
8718 @ref{Installing a library}
8723 In the binder the switch @option{^-I^/SEARCH^}
8724 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8725 is used to specify both source and
8726 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
8727 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
8728 instead if you want to specify
8729 source paths only, and @option{^-aO^/LIBRARY_SEARCH^}
8730 @cindex @option{^-aO^/LIBRARY_SEARCH^} (@command{gnatbind})
8731 if you want to specify library paths
8732 only. This means that for the binder
8733 @option{^-I^/SEARCH=^}@var{dir} is equivalent to
8734 @option{^-aI^/SOURCE_SEARCH=^}@var{dir}
8735 @option{^-aO^/OBJECT_SEARCH=^}@var{dir}.
8736 The binder generates the bind file (a C language source file) in the
8737 current working directory.
8743 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
8744 children make up the GNAT Run-Time Library, together with the package
8745 GNAT and its children, which contain a set of useful additional
8746 library functions provided by GNAT. The sources for these units are
8747 needed by the compiler and are kept together in one directory. The ALI
8748 files and object files generated by compiling the RTL are needed by the
8749 binder and the linker and are kept together in one directory, typically
8750 different from the directory containing the sources. In a normal
8751 installation, you need not specify these directory names when compiling
8752 or binding. Either the environment variables or the built-in defaults
8753 cause these files to be found.
8755 Besides simplifying access to the RTL, a major use of search paths is
8756 in compiling sources from multiple directories. This can make
8757 development environments much more flexible.
8759 @node Examples of gnatbind Usage
8760 @section Examples of @code{gnatbind} Usage
8763 This section contains a number of examples of using the GNAT binding
8764 utility @code{gnatbind}.
8767 @item gnatbind hello
8768 The main program @code{Hello} (source program in @file{hello.adb}) is
8769 bound using the standard switch settings. The generated main program is
8770 @file{b~hello.adb}. This is the normal, default use of the binder.
8773 @item gnatbind hello -o mainprog.adb
8776 @item gnatbind HELLO.ALI /OUTPUT=Mainprog.ADB
8778 The main program @code{Hello} (source program in @file{hello.adb}) is
8779 bound using the standard switch settings. The generated main program is
8780 @file{mainprog.adb} with the associated spec in
8781 @file{mainprog.ads}. Note that you must specify the body here not the
8782 spec, in the case where the output is in Ada. Note that if this option
8783 is used, then linking must be done manually, since gnatlink will not
8784 be able to find the generated file.
8787 @item gnatbind main -C -o mainprog.c -x
8790 @item gnatbind MAIN.ALI /BIND_FILE=C /OUTPUT=Mainprog.C /READ_SOURCES=NONE
8792 The main program @code{Main} (source program in
8793 @file{main.adb}) is bound, excluding source files from the
8794 consistency checking, generating
8795 the file @file{mainprog.c}.
8798 @item gnatbind -x main_program -C -o mainprog.c
8799 This command is exactly the same as the previous example. Switches may
8800 appear anywhere in the command line, and single letter switches may be
8801 combined into a single switch.
8805 @item gnatbind -n math dbase -C -o ada-control.c
8808 @item gnatbind /NOMAIN math dbase /BIND_FILE=C /OUTPUT=ada-control.c
8810 The main program is in a language other than Ada, but calls to
8811 subprograms in packages @code{Math} and @code{Dbase} appear. This call
8812 to @code{gnatbind} generates the file @file{ada-control.c} containing
8813 the @code{adainit} and @code{adafinal} routines to be called before and
8814 after accessing the Ada units.
8817 @c ------------------------------------
8818 @node Linking Using gnatlink
8819 @chapter Linking Using @command{gnatlink}
8820 @c ------------------------------------
8824 This chapter discusses @command{gnatlink}, a tool that links
8825 an Ada program and builds an executable file. This utility
8826 invokes the system linker ^(via the @command{gcc} command)^^
8827 with a correct list of object files and library references.
8828 @command{gnatlink} automatically determines the list of files and
8829 references for the Ada part of a program. It uses the binder file
8830 generated by the @command{gnatbind} to determine this list.
8832 Note: to invoke @code{gnatlink} with a project file, use the @code{gnat}
8833 driver (see @ref{The GNAT Driver and Project Files}).
8836 * Running gnatlink::
8837 * Switches for gnatlink::
8840 @node Running gnatlink
8841 @section Running @command{gnatlink}
8844 The form of the @command{gnatlink} command is
8847 $ gnatlink @ovar{switches} @var{mainprog}@r{[}.ali@r{]}
8848 @ovar{non-Ada objects} @ovar{linker options}
8852 The arguments of @command{gnatlink} (switches, main @file{ALI} file,
8854 or linker options) may be in any order, provided that no non-Ada object may
8855 be mistaken for a main @file{ALI} file.
8856 Any file name @file{F} without the @file{.ali}
8857 extension will be taken as the main @file{ALI} file if a file exists
8858 whose name is the concatenation of @file{F} and @file{.ali}.
8861 @file{@var{mainprog}.ali} references the ALI file of the main program.
8862 The @file{.ali} extension of this file can be omitted. From this
8863 reference, @command{gnatlink} locates the corresponding binder file
8864 @file{b~@var{mainprog}.adb} and, using the information in this file along
8865 with the list of non-Ada objects and linker options, constructs a
8866 linker command file to create the executable.
8868 The arguments other than the @command{gnatlink} switches and the main
8869 @file{ALI} file are passed to the linker uninterpreted.
8870 They typically include the names of
8871 object files for units written in other languages than Ada and any library
8872 references required to resolve references in any of these foreign language
8873 units, or in @code{Import} pragmas in any Ada units.
8875 @var{linker options} is an optional list of linker specific
8877 The default linker called by gnatlink is @command{gcc} which in
8878 turn calls the appropriate system linker.
8879 Standard options for the linker such as @option{-lmy_lib} or
8880 @option{-Ldir} can be added as is.
8881 For options that are not recognized by
8882 @command{gcc} as linker options, use the @command{gcc} switches
8883 @option{-Xlinker} or @option{-Wl,}.
8884 Refer to the GCC documentation for
8885 details. Here is an example showing how to generate a linker map:
8888 $ ^gnatlink my_prog -Wl,-Map,MAPFILE^GNAT LINK my_prog.ali /MAP^
8891 Using @var{linker options} it is possible to set the program stack and
8894 See @ref{Setting Stack Size from gnatlink} and
8895 @ref{Setting Heap Size from gnatlink}.
8898 @command{gnatlink} determines the list of objects required by the Ada
8899 program and prepends them to the list of objects passed to the linker.
8900 @command{gnatlink} also gathers any arguments set by the use of
8901 @code{pragma Linker_Options} and adds them to the list of arguments
8902 presented to the linker.
8905 @command{gnatlink} accepts the following types of extra files on the command
8906 line: objects (@file{.OBJ}), libraries (@file{.OLB}), sharable images
8907 (@file{.EXE}), and options files (@file{.OPT}). These are recognized and
8908 handled according to their extension.
8911 @node Switches for gnatlink
8912 @section Switches for @command{gnatlink}
8915 The following switches are available with the @command{gnatlink} utility:
8921 @cindex @option{--version} @command{gnatlink}
8922 Display Copyright and version, then exit disregarding all other options.
8925 @cindex @option{--help} @command{gnatlink}
8926 If @option{--version} was not used, display usage, then exit disregarding
8929 @item ^-A^/BIND_FILE=ADA^
8930 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatlink})
8931 The binder has generated code in Ada. This is the default.
8933 @item ^-C^/BIND_FILE=C^
8934 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatlink})
8935 If instead of generating a file in Ada, the binder has generated one in
8936 C, then the linker needs to know about it. Use this switch to signal
8937 to @command{gnatlink} that the binder has generated C code rather than
8940 @item ^-f^/FORCE_OBJECT_FILE_LIST^
8941 @cindex Command line length
8942 @cindex @option{^-f^/FORCE_OBJECT_FILE_LIST^} (@command{gnatlink})
8943 On some targets, the command line length is limited, and @command{gnatlink}
8944 will generate a separate file for the linker if the list of object files
8946 The @option{^-f^/FORCE_OBJECT_FILE_LIST^} switch forces this file
8947 to be generated even if
8948 the limit is not exceeded. This is useful in some cases to deal with
8949 special situations where the command line length is exceeded.
8952 @cindex Debugging information, including
8953 @cindex @option{^-g^/DEBUG^} (@command{gnatlink})
8954 The option to include debugging information causes the Ada bind file (in
8955 other words, @file{b~@var{mainprog}.adb}) to be compiled with
8956 @option{^-g^/DEBUG^}.
8957 In addition, the binder does not delete the @file{b~@var{mainprog}.adb},
8958 @file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files.
8959 Without @option{^-g^/DEBUG^}, the binder removes these files by
8960 default. The same procedure apply if a C bind file was generated using
8961 @option{^-C^/BIND_FILE=C^} @code{gnatbind} option, in this case the filenames
8962 are @file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}.
8964 @item ^-n^/NOCOMPILE^
8965 @cindex @option{^-n^/NOCOMPILE^} (@command{gnatlink})
8966 Do not compile the file generated by the binder. This may be used when
8967 a link is rerun with different options, but there is no need to recompile
8971 @cindex @option{^-v^/VERBOSE^} (@command{gnatlink})
8972 Causes additional information to be output, including a full list of the
8973 included object files. This switch option is most useful when you want
8974 to see what set of object files are being used in the link step.
8976 @item ^-v -v^/VERBOSE/VERBOSE^
8977 @cindex @option{^-v -v^/VERBOSE/VERBOSE^} (@command{gnatlink})
8978 Very verbose mode. Requests that the compiler operate in verbose mode when
8979 it compiles the binder file, and that the system linker run in verbose mode.
8981 @item ^-o ^/EXECUTABLE=^@var{exec-name}
8982 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatlink})
8983 @var{exec-name} specifies an alternate name for the generated
8984 executable program. If this switch is omitted, the executable has the same
8985 name as the main unit. For example, @code{gnatlink try.ali} creates
8986 an executable called @file{^try^TRY.EXE^}.
8989 @item -b @var{target}
8990 @cindex @option{-b} (@command{gnatlink})
8991 Compile your program to run on @var{target}, which is the name of a
8992 system configuration. You must have a GNAT cross-compiler built if
8993 @var{target} is not the same as your host system.
8996 @cindex @option{-B} (@command{gnatlink})
8997 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
8998 from @var{dir} instead of the default location. Only use this switch
8999 when multiple versions of the GNAT compiler are available.
9000 @xref{Directory Options,,, gcc, The GNU Compiler Collection},
9001 for further details. You would normally use the @option{-b} or
9002 @option{-V} switch instead.
9004 @item --GCC=@var{compiler_name}
9005 @cindex @option{--GCC=compiler_name} (@command{gnatlink})
9006 Program used for compiling the binder file. The default is
9007 @command{gcc}. You need to use quotes around @var{compiler_name} if
9008 @code{compiler_name} contains spaces or other separator characters.
9009 As an example @option{--GCC="foo -x -y"} will instruct @command{gnatlink} to
9010 use @code{foo -x -y} as your compiler. Note that switch @option{-c} is always
9011 inserted after your command name. Thus in the above example the compiler
9012 command that will be used by @command{gnatlink} will be @code{foo -c -x -y}.
9013 A limitation of this syntax is that the name and path name of the executable
9014 itself must not include any embedded spaces. If the compiler executable is
9015 different from the default one (gcc or <prefix>-gcc), then the back-end
9016 switches in the ALI file are not used to compile the binder generated source.
9017 For example, this is the case with @option{--GCC="foo -x -y"}. But the back end
9018 switches will be used for @option{--GCC="gcc -gnatv"}. If several
9019 @option{--GCC=compiler_name} are used, only the last @var{compiler_name}
9020 is taken into account. However, all the additional switches are also taken
9022 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
9023 @option{--GCC="bar -x -y -z -t"}.
9025 @item --LINK=@var{name}
9026 @cindex @option{--LINK=} (@command{gnatlink})
9027 @var{name} is the name of the linker to be invoked. This is especially
9028 useful in mixed language programs since languages such as C++ require
9029 their own linker to be used. When this switch is omitted, the default
9030 name for the linker is @command{gcc}. When this switch is used, the
9031 specified linker is called instead of @command{gcc} with exactly the same
9032 parameters that would have been passed to @command{gcc} so if the desired
9033 linker requires different parameters it is necessary to use a wrapper
9034 script that massages the parameters before invoking the real linker. It
9035 may be useful to control the exact invocation by using the verbose
9041 @item /DEBUG=TRACEBACK
9042 @cindex @code{/DEBUG=TRACEBACK} (@command{gnatlink})
9043 This qualifier causes sufficient information to be included in the
9044 executable file to allow a traceback, but does not include the full
9045 symbol information needed by the debugger.
9047 @item /IDENTIFICATION="<string>"
9048 @code{"<string>"} specifies the string to be stored in the image file
9049 identification field in the image header.
9050 It overrides any pragma @code{Ident} specified string.
9052 @item /NOINHIBIT-EXEC
9053 Generate the executable file even if there are linker warnings.
9055 @item /NOSTART_FILES
9056 Don't link in the object file containing the ``main'' transfer address.
9057 Used when linking with a foreign language main program compiled with an
9061 Prefer linking with object libraries over sharable images, even without
9067 @node The GNAT Make Program gnatmake
9068 @chapter The GNAT Make Program @command{gnatmake}
9072 * Running gnatmake::
9073 * Switches for gnatmake::
9074 * Mode Switches for gnatmake::
9075 * Notes on the Command Line::
9076 * How gnatmake Works::
9077 * Examples of gnatmake Usage::
9080 A typical development cycle when working on an Ada program consists of
9081 the following steps:
9085 Edit some sources to fix bugs.
9091 Compile all sources affected.
9101 The third step can be tricky, because not only do the modified files
9102 @cindex Dependency rules
9103 have to be compiled, but any files depending on these files must also be
9104 recompiled. The dependency rules in Ada can be quite complex, especially
9105 in the presence of overloading, @code{use} clauses, generics and inlined
9108 @command{gnatmake} automatically takes care of the third and fourth steps
9109 of this process. It determines which sources need to be compiled,
9110 compiles them, and binds and links the resulting object files.
9112 Unlike some other Ada make programs, the dependencies are always
9113 accurately recomputed from the new sources. The source based approach of
9114 the GNAT compilation model makes this possible. This means that if
9115 changes to the source program cause corresponding changes in
9116 dependencies, they will always be tracked exactly correctly by
9119 @node Running gnatmake
9120 @section Running @command{gnatmake}
9123 The usual form of the @command{gnatmake} command is
9126 $ gnatmake @ovar{switches} @var{file_name}
9127 @ovar{file_names} @ovar{mode_switches}
9131 The only required argument is one @var{file_name}, which specifies
9132 a compilation unit that is a main program. Several @var{file_names} can be
9133 specified: this will result in several executables being built.
9134 If @code{switches} are present, they can be placed before the first
9135 @var{file_name}, between @var{file_names} or after the last @var{file_name}.
9136 If @var{mode_switches} are present, they must always be placed after
9137 the last @var{file_name} and all @code{switches}.
9139 If you are using standard file extensions (@file{.adb} and @file{.ads}), then the
9140 extension may be omitted from the @var{file_name} arguments. However, if
9141 you are using non-standard extensions, then it is required that the
9142 extension be given. A relative or absolute directory path can be
9143 specified in a @var{file_name}, in which case, the input source file will
9144 be searched for in the specified directory only. Otherwise, the input
9145 source file will first be searched in the directory where
9146 @command{gnatmake} was invoked and if it is not found, it will be search on
9147 the source path of the compiler as described in
9148 @ref{Search Paths and the Run-Time Library (RTL)}.
9150 All @command{gnatmake} output (except when you specify
9151 @option{^-M^/DEPENDENCIES_LIST^}) is to
9152 @file{stderr}. The output produced by the
9153 @option{^-M^/DEPENDENCIES_LIST^} switch is send to
9156 @node Switches for gnatmake
9157 @section Switches for @command{gnatmake}
9160 You may specify any of the following switches to @command{gnatmake}:
9166 @cindex @option{--version} @command{gnatmake}
9167 Display Copyright and version, then exit disregarding all other options.
9170 @cindex @option{--help} @command{gnatmake}
9171 If @option{--version} was not used, display usage, then exit disregarding
9175 @item --GCC=@var{compiler_name}
9176 @cindex @option{--GCC=compiler_name} (@command{gnatmake})
9177 Program used for compiling. The default is `@command{gcc}'. You need to use
9178 quotes around @var{compiler_name} if @code{compiler_name} contains
9179 spaces or other separator characters. As an example @option{--GCC="foo -x
9180 -y"} will instruct @command{gnatmake} to use @code{foo -x -y} as your
9181 compiler. A limitation of this syntax is that the name and path name of
9182 the executable itself must not include any embedded spaces. Note that
9183 switch @option{-c} is always inserted after your command name. Thus in the
9184 above example the compiler command that will be used by @command{gnatmake}
9185 will be @code{foo -c -x -y}. If several @option{--GCC=compiler_name} are
9186 used, only the last @var{compiler_name} is taken into account. However,
9187 all the additional switches are also taken into account. Thus,
9188 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
9189 @option{--GCC="bar -x -y -z -t"}.
9191 @item --GNATBIND=@var{binder_name}
9192 @cindex @option{--GNATBIND=binder_name} (@command{gnatmake})
9193 Program used for binding. The default is `@code{gnatbind}'. You need to
9194 use quotes around @var{binder_name} if @var{binder_name} contains spaces
9195 or other separator characters. As an example @option{--GNATBIND="bar -x
9196 -y"} will instruct @command{gnatmake} to use @code{bar -x -y} as your
9197 binder. Binder switches that are normally appended by @command{gnatmake}
9198 to `@code{gnatbind}' are now appended to the end of @code{bar -x -y}.
9199 A limitation of this syntax is that the name and path name of the executable
9200 itself must not include any embedded spaces.
9202 @item --GNATLINK=@var{linker_name}
9203 @cindex @option{--GNATLINK=linker_name} (@command{gnatmake})
9204 Program used for linking. The default is `@command{gnatlink}'. You need to
9205 use quotes around @var{linker_name} if @var{linker_name} contains spaces
9206 or other separator characters. As an example @option{--GNATLINK="lan -x
9207 -y"} will instruct @command{gnatmake} to use @code{lan -x -y} as your
9208 linker. Linker switches that are normally appended by @command{gnatmake} to
9209 `@command{gnatlink}' are now appended to the end of @code{lan -x -y}.
9210 A limitation of this syntax is that the name and path name of the executable
9211 itself must not include any embedded spaces.
9215 @item ^-a^/ALL_FILES^
9216 @cindex @option{^-a^/ALL_FILES^} (@command{gnatmake})
9217 Consider all files in the make process, even the GNAT internal system
9218 files (for example, the predefined Ada library files), as well as any
9219 locked files. Locked files are files whose ALI file is write-protected.
9221 @command{gnatmake} does not check these files,
9222 because the assumption is that the GNAT internal files are properly up
9223 to date, and also that any write protected ALI files have been properly
9224 installed. Note that if there is an installation problem, such that one
9225 of these files is not up to date, it will be properly caught by the
9227 You may have to specify this switch if you are working on GNAT
9228 itself. The switch @option{^-a^/ALL_FILES^} is also useful
9229 in conjunction with @option{^-f^/FORCE_COMPILE^}
9230 if you need to recompile an entire application,
9231 including run-time files, using special configuration pragmas,
9232 such as a @code{Normalize_Scalars} pragma.
9235 @code{gnatmake ^-a^/ALL_FILES^} compiles all GNAT
9238 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
9241 the @code{/CHECKS=SUPPRESS_ALL /STYLE_CHECKS=GNAT} switch.
9244 @item ^-b^/ACTIONS=BIND^
9245 @cindex @option{^-b^/ACTIONS=BIND^} (@command{gnatmake})
9246 Bind only. Can be combined with @option{^-c^/ACTIONS=COMPILE^} to do
9247 compilation and binding, but no link.
9248 Can be combined with @option{^-l^/ACTIONS=LINK^}
9249 to do binding and linking. When not combined with
9250 @option{^-c^/ACTIONS=COMPILE^}
9251 all the units in the closure of the main program must have been previously
9252 compiled and must be up to date. The root unit specified by @var{file_name}
9253 may be given without extension, with the source extension or, if no GNAT
9254 Project File is specified, with the ALI file extension.
9256 @item ^-c^/ACTIONS=COMPILE^
9257 @cindex @option{^-c^/ACTIONS=COMPILE^} (@command{gnatmake})
9258 Compile only. Do not perform binding, except when @option{^-b^/ACTIONS=BIND^}
9259 is also specified. Do not perform linking, except if both
9260 @option{^-b^/ACTIONS=BIND^} and
9261 @option{^-l^/ACTIONS=LINK^} are also specified.
9262 If the root unit specified by @var{file_name} is not a main unit, this is the
9263 default. Otherwise @command{gnatmake} will attempt binding and linking
9264 unless all objects are up to date and the executable is more recent than
9268 @cindex @option{^-C^/MAPPING^} (@command{gnatmake})
9269 Use a temporary mapping file. A mapping file is a way to communicate to the
9270 compiler two mappings: from unit names to file names (without any directory
9271 information) and from file names to path names (with full directory
9272 information). These mappings are used by the compiler to short-circuit the path
9273 search. When @command{gnatmake} is invoked with this switch, it will create
9274 a temporary mapping file, initially populated by the project manager,
9275 if @option{^-P^/PROJECT_FILE^} is used, otherwise initially empty.
9276 Each invocation of the compiler will add the newly accessed sources to the
9277 mapping file. This will improve the source search during the next invocation
9280 @item ^-C=^/USE_MAPPING_FILE=^@var{file}
9281 @cindex @option{^-C=^/USE_MAPPING^} (@command{gnatmake})
9282 Use a specific mapping file. The file, specified as a path name (absolute or
9283 relative) by this switch, should already exist, otherwise the switch is
9284 ineffective. The specified mapping file will be communicated to the compiler.
9285 This switch is not compatible with a project file
9286 (^-P^/PROJECT_FILE=^@var{file}) or with multiple compiling processes
9287 (^-j^/PROCESSES=^nnn, when nnn is greater than 1).
9289 @item ^-d^/DISPLAY_PROGRESS^
9290 @cindex @option{^-d^/DISPLAY_PROGRESS^} (@command{gnatmake})
9291 Display progress for each source, up to date or not, as a single line
9294 completed x out of y (zz%)
9297 If the file needs to be compiled this is displayed after the invocation of
9298 the compiler. These lines are displayed even in quiet output mode.
9300 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
9301 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@command{gnatmake})
9302 Put all object files and ALI file in directory @var{dir}.
9303 If the @option{^-D^/DIRECTORY_OBJECTS^} switch is not used, all object files
9304 and ALI files go in the current working directory.
9306 This switch cannot be used when using a project file.
9310 @cindex @option{-eL} (@command{gnatmake})
9311 Follow all symbolic links when processing project files.
9314 @item ^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^
9315 @cindex @option{^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^} (@command{gnatmake})
9316 Output the commands for the compiler, the binder and the linker
9317 on ^standard output^SYS$OUTPUT^,
9318 instead of ^standard error^SYS$ERROR^.
9320 @item ^-f^/FORCE_COMPILE^
9321 @cindex @option{^-f^/FORCE_COMPILE^} (@command{gnatmake})
9322 Force recompilations. Recompile all sources, even though some object
9323 files may be up to date, but don't recompile predefined or GNAT internal
9324 files or locked files (files with a write-protected ALI file),
9325 unless the @option{^-a^/ALL_FILES^} switch is also specified.
9327 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
9328 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@command{gnatmake})
9329 When using project files, if some errors or warnings are detected during
9330 parsing and verbose mode is not in effect (no use of switch
9331 ^-v^/VERBOSE^), then error lines start with the full path name of the project
9332 file, rather than its simple file name.
9335 @cindex @option{^-g^/DEBUG^} (@command{gnatmake})
9336 Enable debugging. This switch is simply passed to the compiler and to the
9339 @item ^-i^/IN_PLACE^
9340 @cindex @option{^-i^/IN_PLACE^} (@command{gnatmake})
9341 In normal mode, @command{gnatmake} compiles all object files and ALI files
9342 into the current directory. If the @option{^-i^/IN_PLACE^} switch is used,
9343 then instead object files and ALI files that already exist are overwritten
9344 in place. This means that once a large project is organized into separate
9345 directories in the desired manner, then @command{gnatmake} will automatically
9346 maintain and update this organization. If no ALI files are found on the
9347 Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}),
9348 the new object and ALI files are created in the
9349 directory containing the source being compiled. If another organization
9350 is desired, where objects and sources are kept in different directories,
9351 a useful technique is to create dummy ALI files in the desired directories.
9352 When detecting such a dummy file, @command{gnatmake} will be forced to
9353 recompile the corresponding source file, and it will be put the resulting
9354 object and ALI files in the directory where it found the dummy file.
9356 @item ^-j^/PROCESSES=^@var{n}
9357 @cindex @option{^-j^/PROCESSES^} (@command{gnatmake})
9358 @cindex Parallel make
9359 Use @var{n} processes to carry out the (re)compilations. On a
9360 multiprocessor machine compilations will occur in parallel. In the
9361 event of compilation errors, messages from various compilations might
9362 get interspersed (but @command{gnatmake} will give you the full ordered
9363 list of failing compiles at the end). If this is problematic, rerun
9364 the make process with n set to 1 to get a clean list of messages.
9366 @item ^-k^/CONTINUE_ON_ERROR^
9367 @cindex @option{^-k^/CONTINUE_ON_ERROR^} (@command{gnatmake})
9368 Keep going. Continue as much as possible after a compilation error. To
9369 ease the programmer's task in case of compilation errors, the list of
9370 sources for which the compile fails is given when @command{gnatmake}
9373 If @command{gnatmake} is invoked with several @file{file_names} and with this
9374 switch, if there are compilation errors when building an executable,
9375 @command{gnatmake} will not attempt to build the following executables.
9377 @item ^-l^/ACTIONS=LINK^
9378 @cindex @option{^-l^/ACTIONS=LINK^} (@command{gnatmake})
9379 Link only. Can be combined with @option{^-b^/ACTIONS=BIND^} to binding
9380 and linking. Linking will not be performed if combined with
9381 @option{^-c^/ACTIONS=COMPILE^}
9382 but not with @option{^-b^/ACTIONS=BIND^}.
9383 When not combined with @option{^-b^/ACTIONS=BIND^}
9384 all the units in the closure of the main program must have been previously
9385 compiled and must be up to date, and the main program needs to have been bound.
9386 The root unit specified by @var{file_name}
9387 may be given without extension, with the source extension or, if no GNAT
9388 Project File is specified, with the ALI file extension.
9390 @item ^-m^/MINIMAL_RECOMPILATION^
9391 @cindex @option{^-m^/MINIMAL_RECOMPILATION^} (@command{gnatmake})
9392 Specify that the minimum necessary amount of recompilations
9393 be performed. In this mode @command{gnatmake} ignores time
9394 stamp differences when the only
9395 modifications to a source file consist in adding/removing comments,
9396 empty lines, spaces or tabs. This means that if you have changed the
9397 comments in a source file or have simply reformatted it, using this
9398 switch will tell @command{gnatmake} not to recompile files that depend on it
9399 (provided other sources on which these files depend have undergone no
9400 semantic modifications). Note that the debugging information may be
9401 out of date with respect to the sources if the @option{-m} switch causes
9402 a compilation to be switched, so the use of this switch represents a
9403 trade-off between compilation time and accurate debugging information.
9405 @item ^-M^/DEPENDENCIES_LIST^
9406 @cindex Dependencies, producing list
9407 @cindex @option{^-M^/DEPENDENCIES_LIST^} (@command{gnatmake})
9408 Check if all objects are up to date. If they are, output the object
9409 dependences to @file{stdout} in a form that can be directly exploited in
9410 a @file{Makefile}. By default, each source file is prefixed with its
9411 (relative or absolute) directory name. This name is whatever you
9412 specified in the various @option{^-aI^/SOURCE_SEARCH^}
9413 and @option{^-I^/SEARCH^} switches. If you use
9414 @code{gnatmake ^-M^/DEPENDENCIES_LIST^}
9415 @option{^-q^/QUIET^}
9416 (see below), only the source file names,
9417 without relative paths, are output. If you just specify the
9418 @option{^-M^/DEPENDENCIES_LIST^}
9419 switch, dependencies of the GNAT internal system files are omitted. This
9420 is typically what you want. If you also specify
9421 the @option{^-a^/ALL_FILES^} switch,
9422 dependencies of the GNAT internal files are also listed. Note that
9423 dependencies of the objects in external Ada libraries (see switch
9424 @option{^-aL^/SKIP_MISSING=^}@var{dir} in the following list)
9427 @item ^-n^/DO_OBJECT_CHECK^
9428 @cindex @option{^-n^/DO_OBJECT_CHECK^} (@command{gnatmake})
9429 Don't compile, bind, or link. Checks if all objects are up to date.
9430 If they are not, the full name of the first file that needs to be
9431 recompiled is printed.
9432 Repeated use of this option, followed by compiling the indicated source
9433 file, will eventually result in recompiling all required units.
9435 @item ^-o ^/EXECUTABLE=^@var{exec_name}
9436 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatmake})
9437 Output executable name. The name of the final executable program will be
9438 @var{exec_name}. If the @option{^-o^/EXECUTABLE^} switch is omitted the default
9439 name for the executable will be the name of the input file in appropriate form
9440 for an executable file on the host system.
9442 This switch cannot be used when invoking @command{gnatmake} with several
9445 @item ^-p or --create-missing-dirs^/CREATE_MISSING_DIRS^
9446 @cindex @option{^-p^/CREATE_MISSING_DIRS^} (@command{gnatmake})
9447 When using project files (^-P^/PROJECT_FILE=^@var{project}), create
9448 automatically missing object directories, library directories and exec
9451 @item ^-P^/PROJECT_FILE=^@var{project}
9452 @cindex @option{^-P^/PROJECT_FILE^} (@command{gnatmake})
9453 Use project file @var{project}. Only one such switch can be used.
9454 @xref{gnatmake and Project Files}.
9457 @cindex @option{^-q^/QUIET^} (@command{gnatmake})
9458 Quiet. When this flag is not set, the commands carried out by
9459 @command{gnatmake} are displayed.
9461 @item ^-s^/SWITCH_CHECK/^
9462 @cindex @option{^-s^/SWITCH_CHECK^} (@command{gnatmake})
9463 Recompile if compiler switches have changed since last compilation.
9464 All compiler switches but -I and -o are taken into account in the
9466 orders between different ``first letter'' switches are ignored, but
9467 orders between same switches are taken into account. For example,
9468 @option{-O -O2} is different than @option{-O2 -O}, but @option{-g -O}
9469 is equivalent to @option{-O -g}.
9471 This switch is recommended when Integrated Preprocessing is used.
9474 @cindex @option{^-u^/UNIQUE^} (@command{gnatmake})
9475 Unique. Recompile at most the main files. It implies -c. Combined with
9476 -f, it is equivalent to calling the compiler directly. Note that using
9477 ^-u^/UNIQUE^ with a project file and no main has a special meaning
9478 (@pxref{Project Files and Main Subprograms}).
9480 @item ^-U^/ALL_PROJECTS^
9481 @cindex @option{^-U^/ALL_PROJECTS^} (@command{gnatmake})
9482 When used without a project file or with one or several mains on the command
9483 line, is equivalent to ^-u^/UNIQUE^. When used with a project file and no main
9484 on the command line, all sources of all project files are checked and compiled
9485 if not up to date, and libraries are rebuilt, if necessary.
9488 @cindex @option{^-v^/REASONS^} (@command{gnatmake})
9489 Verbose. Display the reason for all recompilations @command{gnatmake}
9490 decides are necessary, with the highest verbosity level.
9492 @item ^-vl^/LOW_VERBOSITY^
9493 @cindex @option{^-vl^/LOW_VERBOSITY^} (@command{gnatmake})
9494 Verbosity level Low. Display fewer lines than in verbosity Medium.
9496 @item ^-vm^/MEDIUM_VERBOSITY^
9497 @cindex @option{^-vm^/MEDIUM_VERBOSITY^} (@command{gnatmake})
9498 Verbosity level Medium. Potentially display fewer lines than in verbosity High.
9500 @item ^-vh^/HIGH_VERBOSITY^
9501 @cindex @option{^-vm^/HIGH_VERBOSITY^} (@command{gnatmake})
9502 Verbosity level High. Equivalent to ^-v^/REASONS^.
9504 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
9505 Indicate the verbosity of the parsing of GNAT project files.
9506 @xref{Switches Related to Project Files}.
9508 @item ^-x^/NON_PROJECT_UNIT_COMPILATION^
9509 @cindex @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} (@command{gnatmake})
9510 Indicate that sources that are not part of any Project File may be compiled.
9511 Normally, when using Project Files, only sources that are part of a Project
9512 File may be compile. When this switch is used, a source outside of all Project
9513 Files may be compiled. The ALI file and the object file will be put in the
9514 object directory of the main Project. The compilation switches used will only
9515 be those specified on the command line. Even when
9516 @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} is used, mains specified on the
9517 command line need to be sources of a project file.
9519 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
9520 Indicate that external variable @var{name} has the value @var{value}.
9521 The Project Manager will use this value for occurrences of
9522 @code{external(name)} when parsing the project file.
9523 @xref{Switches Related to Project Files}.
9526 @cindex @option{^-z^/NOMAIN^} (@command{gnatmake})
9527 No main subprogram. Bind and link the program even if the unit name
9528 given on the command line is a package name. The resulting executable
9529 will execute the elaboration routines of the package and its closure,
9530 then the finalization routines.
9535 @item @command{gcc} @asis{switches}
9537 Any uppercase or multi-character switch that is not a @command{gnatmake} switch
9538 is passed to @command{gcc} (e.g.@: @option{-O}, @option{-gnato,} etc.)
9541 Any qualifier that cannot be recognized as a qualifier for @code{GNAT MAKE}
9542 but is recognizable as a valid qualifier for @code{GNAT COMPILE} is
9543 automatically treated as a compiler switch, and passed on to all
9544 compilations that are carried out.
9549 Source and library search path switches:
9553 @item ^-aI^/SOURCE_SEARCH=^@var{dir}
9554 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatmake})
9555 When looking for source files also look in directory @var{dir}.
9556 The order in which source files search is undertaken is
9557 described in @ref{Search Paths and the Run-Time Library (RTL)}.
9559 @item ^-aL^/SKIP_MISSING=^@var{dir}
9560 @cindex @option{^-aL^/SKIP_MISSING^} (@command{gnatmake})
9561 Consider @var{dir} as being an externally provided Ada library.
9562 Instructs @command{gnatmake} to skip compilation units whose @file{.ALI}
9563 files have been located in directory @var{dir}. This allows you to have
9564 missing bodies for the units in @var{dir} and to ignore out of date bodies
9565 for the same units. You still need to specify
9566 the location of the specs for these units by using the switches
9567 @option{^-aI^/SOURCE_SEARCH=^@var{dir}}
9568 or @option{^-I^/SEARCH=^@var{dir}}.
9569 Note: this switch is provided for compatibility with previous versions
9570 of @command{gnatmake}. The easier method of causing standard libraries
9571 to be excluded from consideration is to write-protect the corresponding
9574 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
9575 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatmake})
9576 When searching for library and object files, look in directory
9577 @var{dir}. The order in which library files are searched is described in
9578 @ref{Search Paths for gnatbind}.
9580 @item ^-A^/CONDITIONAL_SOURCE_SEARCH=^@var{dir}
9581 @cindex Search paths, for @command{gnatmake}
9582 @cindex @option{^-A^/CONDITIONAL_SOURCE_SEARCH^} (@command{gnatmake})
9583 Equivalent to @option{^-aL^/SKIP_MISSING=^@var{dir}
9584 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9586 @item ^-I^/SEARCH=^@var{dir}
9587 @cindex @option{^-I^/SEARCH^} (@command{gnatmake})
9588 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}
9589 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9591 @item ^-I-^/NOCURRENT_DIRECTORY^
9592 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatmake})
9593 @cindex Source files, suppressing search
9594 Do not look for source files in the directory containing the source
9595 file named in the command line.
9596 Do not look for ALI or object files in the directory
9597 where @command{gnatmake} was invoked.
9599 @item ^-L^/LIBRARY_SEARCH=^@var{dir}
9600 @cindex @option{^-L^/LIBRARY_SEARCH^} (@command{gnatmake})
9601 @cindex Linker libraries
9602 Add directory @var{dir} to the list of directories in which the linker
9603 will search for libraries. This is equivalent to
9604 @option{-largs ^-L^/LIBRARY_SEARCH=^}@var{dir}.
9606 Furthermore, under Windows, the sources pointed to by the libraries path
9607 set in the registry are not searched for.
9611 @cindex @option{-nostdinc} (@command{gnatmake})
9612 Do not look for source files in the system default directory.
9615 @cindex @option{-nostdlib} (@command{gnatmake})
9616 Do not look for library files in the system default directory.
9618 @item --RTS=@var{rts-path}
9619 @cindex @option{--RTS} (@command{gnatmake})
9620 Specifies the default location of the runtime library. GNAT looks for the
9622 in the following directories, and stops as soon as a valid runtime is found
9623 (@file{adainclude} or @file{ada_source_path}, and @file{adalib} or
9624 @file{ada_object_path} present):
9627 @item <current directory>/$rts_path
9629 @item <default-search-dir>/$rts_path
9631 @item <default-search-dir>/rts-$rts_path
9635 The selected path is handled like a normal RTS path.
9639 @node Mode Switches for gnatmake
9640 @section Mode Switches for @command{gnatmake}
9643 The mode switches (referred to as @code{mode_switches}) allow the
9644 inclusion of switches that are to be passed to the compiler itself, the
9645 binder or the linker. The effect of a mode switch is to cause all
9646 subsequent switches up to the end of the switch list, or up to the next
9647 mode switch, to be interpreted as switches to be passed on to the
9648 designated component of GNAT.
9652 @item -cargs @var{switches}
9653 @cindex @option{-cargs} (@command{gnatmake})
9654 Compiler switches. Here @var{switches} is a list of switches
9655 that are valid switches for @command{gcc}. They will be passed on to
9656 all compile steps performed by @command{gnatmake}.
9658 @item -bargs @var{switches}
9659 @cindex @option{-bargs} (@command{gnatmake})
9660 Binder switches. Here @var{switches} is a list of switches
9661 that are valid switches for @code{gnatbind}. They will be passed on to
9662 all bind steps performed by @command{gnatmake}.
9664 @item -largs @var{switches}
9665 @cindex @option{-largs} (@command{gnatmake})
9666 Linker switches. Here @var{switches} is a list of switches
9667 that are valid switches for @command{gnatlink}. They will be passed on to
9668 all link steps performed by @command{gnatmake}.
9670 @item -margs @var{switches}
9671 @cindex @option{-margs} (@command{gnatmake})
9672 Make switches. The switches are directly interpreted by @command{gnatmake},
9673 regardless of any previous occurrence of @option{-cargs}, @option{-bargs}
9677 @node Notes on the Command Line
9678 @section Notes on the Command Line
9681 This section contains some additional useful notes on the operation
9682 of the @command{gnatmake} command.
9686 @cindex Recompilation, by @command{gnatmake}
9687 If @command{gnatmake} finds no ALI files, it recompiles the main program
9688 and all other units required by the main program.
9689 This means that @command{gnatmake}
9690 can be used for the initial compile, as well as during subsequent steps of
9691 the development cycle.
9694 If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb}
9695 is a subunit or body of a generic unit, @command{gnatmake} recompiles
9696 @file{@var{file}.adb} (because it finds no ALI) and stops, issuing a
9700 In @command{gnatmake} the switch @option{^-I^/SEARCH^}
9701 is used to specify both source and
9702 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
9703 instead if you just want to specify
9704 source paths only and @option{^-aO^/OBJECT_SEARCH^}
9705 if you want to specify library paths
9709 @command{gnatmake} will ignore any files whose ALI file is write-protected.
9710 This may conveniently be used to exclude standard libraries from
9711 consideration and in particular it means that the use of the
9712 @option{^-f^/FORCE_COMPILE^} switch will not recompile these files
9713 unless @option{^-a^/ALL_FILES^} is also specified.
9716 @command{gnatmake} has been designed to make the use of Ada libraries
9717 particularly convenient. Assume you have an Ada library organized
9718 as follows: @i{^obj-dir^[OBJ_DIR]^} contains the objects and ALI files for
9719 of your Ada compilation units,
9720 whereas @i{^include-dir^[INCLUDE_DIR]^} contains the
9721 specs of these units, but no bodies. Then to compile a unit
9722 stored in @code{main.adb}, which uses this Ada library you would just type
9726 $ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main
9729 $ gnatmake /SOURCE_SEARCH=@i{[INCLUDE_DIR]}
9730 /SKIP_MISSING=@i{[OBJ_DIR]} main
9735 Using @command{gnatmake} along with the
9736 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}
9737 switch provides a mechanism for avoiding unnecessary recompilations. Using
9739 you can update the comments/format of your
9740 source files without having to recompile everything. Note, however, that
9741 adding or deleting lines in a source files may render its debugging
9742 info obsolete. If the file in question is a spec, the impact is rather
9743 limited, as that debugging info will only be useful during the
9744 elaboration phase of your program. For bodies the impact can be more
9745 significant. In all events, your debugger will warn you if a source file
9746 is more recent than the corresponding object, and alert you to the fact
9747 that the debugging information may be out of date.
9750 @node How gnatmake Works
9751 @section How @command{gnatmake} Works
9754 Generally @command{gnatmake} automatically performs all necessary
9755 recompilations and you don't need to worry about how it works. However,
9756 it may be useful to have some basic understanding of the @command{gnatmake}
9757 approach and in particular to understand how it uses the results of
9758 previous compilations without incorrectly depending on them.
9760 First a definition: an object file is considered @dfn{up to date} if the
9761 corresponding ALI file exists and if all the source files listed in the
9762 dependency section of this ALI file have time stamps matching those in
9763 the ALI file. This means that neither the source file itself nor any
9764 files that it depends on have been modified, and hence there is no need
9765 to recompile this file.
9767 @command{gnatmake} works by first checking if the specified main unit is up
9768 to date. If so, no compilations are required for the main unit. If not,
9769 @command{gnatmake} compiles the main program to build a new ALI file that
9770 reflects the latest sources. Then the ALI file of the main unit is
9771 examined to find all the source files on which the main program depends,
9772 and @command{gnatmake} recursively applies the above procedure on all these
9775 This process ensures that @command{gnatmake} only trusts the dependencies
9776 in an existing ALI file if they are known to be correct. Otherwise it
9777 always recompiles to determine a new, guaranteed accurate set of
9778 dependencies. As a result the program is compiled ``upside down'' from what may
9779 be more familiar as the required order of compilation in some other Ada
9780 systems. In particular, clients are compiled before the units on which
9781 they depend. The ability of GNAT to compile in any order is critical in
9782 allowing an order of compilation to be chosen that guarantees that
9783 @command{gnatmake} will recompute a correct set of new dependencies if
9786 When invoking @command{gnatmake} with several @var{file_names}, if a unit is
9787 imported by several of the executables, it will be recompiled at most once.
9789 Note: when using non-standard naming conventions
9790 (@pxref{Using Other File Names}), changing through a configuration pragmas
9791 file the version of a source and invoking @command{gnatmake} to recompile may
9792 have no effect, if the previous version of the source is still accessible
9793 by @command{gnatmake}. It may be necessary to use the switch
9794 ^-f^/FORCE_COMPILE^.
9796 @node Examples of gnatmake Usage
9797 @section Examples of @command{gnatmake} Usage
9800 @item gnatmake hello.adb
9801 Compile all files necessary to bind and link the main program
9802 @file{hello.adb} (containing unit @code{Hello}) and bind and link the
9803 resulting object files to generate an executable file @file{^hello^HELLO.EXE^}.
9805 @item gnatmake main1 main2 main3
9806 Compile all files necessary to bind and link the main programs
9807 @file{main1.adb} (containing unit @code{Main1}), @file{main2.adb}
9808 (containing unit @code{Main2}) and @file{main3.adb}
9809 (containing unit @code{Main3}) and bind and link the resulting object files
9810 to generate three executable files @file{^main1^MAIN1.EXE^},
9811 @file{^main2^MAIN2.EXE^}
9812 and @file{^main3^MAIN3.EXE^}.
9815 @item gnatmake -q Main_Unit -cargs -O2 -bargs -l
9819 @item gnatmake Main_Unit /QUIET
9820 /COMPILER_QUALIFIERS /OPTIMIZE=ALL
9821 /BINDER_QUALIFIERS /ORDER_OF_ELABORATION
9823 Compile all files necessary to bind and link the main program unit
9824 @code{Main_Unit} (from file @file{main_unit.adb}). All compilations will
9825 be done with optimization level 2 and the order of elaboration will be
9826 listed by the binder. @command{gnatmake} will operate in quiet mode, not
9827 displaying commands it is executing.
9830 @c *************************
9831 @node Improving Performance
9832 @chapter Improving Performance
9833 @cindex Improving performance
9836 This chapter presents several topics related to program performance.
9837 It first describes some of the tradeoffs that need to be considered
9838 and some of the techniques for making your program run faster.
9839 It then documents the @command{gnatelim} tool and unused subprogram/data
9840 elimination feature, which can reduce the size of program executables.
9842 Note: to invoke @command{gnatelim} with a project file, use the @code{gnat}
9843 driver (see @ref{The GNAT Driver and Project Files}).
9847 * Performance Considerations::
9848 * Text_IO Suggestions::
9849 * Reducing Size of Ada Executables with gnatelim::
9850 * Reducing Size of Executables with unused subprogram/data elimination::
9854 @c *****************************
9855 @node Performance Considerations
9856 @section Performance Considerations
9859 The GNAT system provides a number of options that allow a trade-off
9864 performance of the generated code
9867 speed of compilation
9870 minimization of dependences and recompilation
9873 the degree of run-time checking.
9877 The defaults (if no options are selected) aim at improving the speed
9878 of compilation and minimizing dependences, at the expense of performance
9879 of the generated code:
9886 no inlining of subprogram calls
9889 all run-time checks enabled except overflow and elaboration checks
9893 These options are suitable for most program development purposes. This
9894 chapter describes how you can modify these choices, and also provides
9895 some guidelines on debugging optimized code.
9898 * Controlling Run-Time Checks::
9899 * Use of Restrictions::
9900 * Optimization Levels::
9901 * Debugging Optimized Code::
9902 * Inlining of Subprograms::
9903 * Other Optimization Switches::
9904 * Optimization and Strict Aliasing::
9907 * Coverage Analysis::
9911 @node Controlling Run-Time Checks
9912 @subsection Controlling Run-Time Checks
9915 By default, GNAT generates all run-time checks, except integer overflow
9916 checks, stack overflow checks, and checks for access before elaboration on
9917 subprogram calls. The latter are not required in default mode, because all
9918 necessary checking is done at compile time.
9919 @cindex @option{-gnatp} (@command{gcc})
9920 @cindex @option{-gnato} (@command{gcc})
9921 Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to
9922 be modified. @xref{Run-Time Checks}.
9924 Our experience is that the default is suitable for most development
9927 We treat integer overflow specially because these
9928 are quite expensive and in our experience are not as important as other
9929 run-time checks in the development process. Note that division by zero
9930 is not considered an overflow check, and divide by zero checks are
9931 generated where required by default.
9933 Elaboration checks are off by default, and also not needed by default, since
9934 GNAT uses a static elaboration analysis approach that avoids the need for
9935 run-time checking. This manual contains a full chapter discussing the issue
9936 of elaboration checks, and if the default is not satisfactory for your use,
9937 you should read this chapter.
9939 For validity checks, the minimal checks required by the Ada Reference
9940 Manual (for case statements and assignments to array elements) are on
9941 by default. These can be suppressed by use of the @option{-gnatVn} switch.
9942 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
9943 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
9944 it may be reasonable to routinely use @option{-gnatVn}. Validity checks
9945 are also suppressed entirely if @option{-gnatp} is used.
9947 @cindex Overflow checks
9948 @cindex Checks, overflow
9951 @cindex pragma Suppress
9952 @cindex pragma Unsuppress
9953 Note that the setting of the switches controls the default setting of
9954 the checks. They may be modified using either @code{pragma Suppress} (to
9955 remove checks) or @code{pragma Unsuppress} (to add back suppressed
9956 checks) in the program source.
9958 @node Use of Restrictions
9959 @subsection Use of Restrictions
9962 The use of pragma Restrictions allows you to control which features are
9963 permitted in your program. Apart from the obvious point that if you avoid
9964 relatively expensive features like finalization (enforceable by the use
9965 of pragma Restrictions (No_Finalization), the use of this pragma does not
9966 affect the generated code in most cases.
9968 One notable exception to this rule is that the possibility of task abort
9969 results in some distributed overhead, particularly if finalization or
9970 exception handlers are used. The reason is that certain sections of code
9971 have to be marked as non-abortable.
9973 If you use neither the @code{abort} statement, nor asynchronous transfer
9974 of control (@code{select @dots{} then abort}), then this distributed overhead
9975 is removed, which may have a general positive effect in improving
9976 overall performance. Especially code involving frequent use of tasking
9977 constructs and controlled types will show much improved performance.
9978 The relevant restrictions pragmas are
9980 @smallexample @c ada
9981 pragma Restrictions (No_Abort_Statements);
9982 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
9986 It is recommended that these restriction pragmas be used if possible. Note
9987 that this also means that you can write code without worrying about the
9988 possibility of an immediate abort at any point.
9990 @node Optimization Levels
9991 @subsection Optimization Levels
9992 @cindex @option{^-O^/OPTIMIZE^} (@command{gcc})
9995 Without any optimization ^option,^qualifier,^
9996 the compiler's goal is to reduce the cost of
9997 compilation and to make debugging produce the expected results.
9998 Statements are independent: if you stop the program with a breakpoint between
9999 statements, you can then assign a new value to any variable or change
10000 the program counter to any other statement in the subprogram and get exactly
10001 the results you would expect from the source code.
10003 Turning on optimization makes the compiler attempt to improve the
10004 performance and/or code size at the expense of compilation time and
10005 possibly the ability to debug the program.
10007 If you use multiple
10008 ^-O options, with or without level numbers,^/OPTIMIZE qualifiers,^
10009 the last such option is the one that is effective.
10012 The default is optimization off. This results in the fastest compile
10013 times, but GNAT makes absolutely no attempt to optimize, and the
10014 generated programs are considerably larger and slower than when
10015 optimization is enabled. You can use the
10017 @option{-O} switch (the permitted forms are @option{-O0}, @option{-O1}
10018 @option{-O2}, @option{-O3}, and @option{-Os})
10021 @code{OPTIMIZE} qualifier
10023 to @command{gcc} to control the optimization level:
10026 @item ^-O0^/OPTIMIZE=NONE^
10027 No optimization (the default);
10028 generates unoptimized code but has
10029 the fastest compilation time.
10031 Note that many other compilers do fairly extensive optimization
10032 even if ``no optimization'' is specified. With gcc, it is
10033 very unusual to use ^-O0^/OPTIMIZE=NONE^ for production if
10034 execution time is of any concern, since ^-O0^/OPTIMIZE=NONE^
10035 really does mean no optimization at all. This difference between
10036 gcc and other compilers should be kept in mind when doing
10037 performance comparisons.
10039 @item ^-O1^/OPTIMIZE=SOME^
10040 Moderate optimization;
10041 optimizes reasonably well but does not
10042 degrade compilation time significantly.
10044 @item ^-O2^/OPTIMIZE=ALL^
10046 @itemx /OPTIMIZE=DEVELOPMENT
10049 generates highly optimized code and has
10050 the slowest compilation time.
10052 @item ^-O3^/OPTIMIZE=INLINING^
10053 Full optimization as in @option{-O2},
10054 and also attempts automatic inlining of small
10055 subprograms within a unit (@pxref{Inlining of Subprograms}).
10057 @item ^-Os^/OPTIMIZE=SPACE^
10058 Optimize space usage of resulting program.
10062 Higher optimization levels perform more global transformations on the
10063 program and apply more expensive analysis algorithms in order to generate
10064 faster and more compact code. The price in compilation time, and the
10065 resulting improvement in execution time,
10066 both depend on the particular application and the hardware environment.
10067 You should experiment to find the best level for your application.
10069 Since the precise set of optimizations done at each level will vary from
10070 release to release (and sometime from target to target), it is best to think
10071 of the optimization settings in general terms.
10072 @xref{Optimize Options,, Options That Control Optimization, gcc, Using
10073 the GNU Compiler Collection (GCC)}, for details about
10074 ^the @option{-O} settings and a number of @option{-f} options that^how to^
10075 individually enable or disable specific optimizations.
10077 Unlike some other compilation systems, ^@command{gcc}^GNAT^ has
10078 been tested extensively at all optimization levels. There are some bugs
10079 which appear only with optimization turned on, but there have also been
10080 bugs which show up only in @emph{unoptimized} code. Selecting a lower
10081 level of optimization does not improve the reliability of the code
10082 generator, which in practice is highly reliable at all optimization
10085 Note regarding the use of @option{-O3}: The use of this optimization level
10086 is generally discouraged with GNAT, since it often results in larger
10087 executables which run more slowly. See further discussion of this point
10088 in @ref{Inlining of Subprograms}.
10090 @node Debugging Optimized Code
10091 @subsection Debugging Optimized Code
10092 @cindex Debugging optimized code
10093 @cindex Optimization and debugging
10096 Although it is possible to do a reasonable amount of debugging at
10098 nonzero optimization levels,
10099 the higher the level the more likely that
10102 @option{/OPTIMIZE} settings other than @code{NONE},
10103 such settings will make it more likely that
10105 source-level constructs will have been eliminated by optimization.
10106 For example, if a loop is strength-reduced, the loop
10107 control variable may be completely eliminated and thus cannot be
10108 displayed in the debugger.
10109 This can only happen at @option{-O2} or @option{-O3}.
10110 Explicit temporary variables that you code might be eliminated at
10111 ^level^setting^ @option{-O1} or higher.
10113 The use of the @option{^-g^/DEBUG^} switch,
10114 @cindex @option{^-g^/DEBUG^} (@command{gcc})
10115 which is needed for source-level debugging,
10116 affects the size of the program executable on disk,
10117 and indeed the debugging information can be quite large.
10118 However, it has no effect on the generated code (and thus does not
10119 degrade performance)
10121 Since the compiler generates debugging tables for a compilation unit before
10122 it performs optimizations, the optimizing transformations may invalidate some
10123 of the debugging data. You therefore need to anticipate certain
10124 anomalous situations that may arise while debugging optimized code.
10125 These are the most common cases:
10129 @i{The ``hopping Program Counter'':} Repeated @code{step} or @code{next}
10131 the PC bouncing back and forth in the code. This may result from any of
10132 the following optimizations:
10136 @i{Common subexpression elimination:} using a single instance of code for a
10137 quantity that the source computes several times. As a result you
10138 may not be able to stop on what looks like a statement.
10141 @i{Invariant code motion:} moving an expression that does not change within a
10142 loop, to the beginning of the loop.
10145 @i{Instruction scheduling:} moving instructions so as to
10146 overlap loads and stores (typically) with other code, or in
10147 general to move computations of values closer to their uses. Often
10148 this causes you to pass an assignment statement without the assignment
10149 happening and then later bounce back to the statement when the
10150 value is actually needed. Placing a breakpoint on a line of code
10151 and then stepping over it may, therefore, not always cause all the
10152 expected side-effects.
10156 @i{The ``big leap'':} More commonly known as @emph{cross-jumping}, in which
10157 two identical pieces of code are merged and the program counter suddenly
10158 jumps to a statement that is not supposed to be executed, simply because
10159 it (and the code following) translates to the same thing as the code
10160 that @emph{was} supposed to be executed. This effect is typically seen in
10161 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
10162 a @code{break} in a C @code{^switch^switch^} statement.
10165 @i{The ``roving variable'':} The symptom is an unexpected value in a variable.
10166 There are various reasons for this effect:
10170 In a subprogram prologue, a parameter may not yet have been moved to its
10174 A variable may be dead, and its register re-used. This is
10175 probably the most common cause.
10178 As mentioned above, the assignment of a value to a variable may
10182 A variable may be eliminated entirely by value propagation or
10183 other means. In this case, GCC may incorrectly generate debugging
10184 information for the variable
10188 In general, when an unexpected value appears for a local variable or parameter
10189 you should first ascertain if that value was actually computed by
10190 your program, as opposed to being incorrectly reported by the debugger.
10192 array elements in an object designated by an access value
10193 are generally less of a problem, once you have ascertained that the access
10195 Typically, this means checking variables in the preceding code and in the
10196 calling subprogram to verify that the value observed is explainable from other
10197 values (one must apply the procedure recursively to those
10198 other values); or re-running the code and stopping a little earlier
10199 (perhaps before the call) and stepping to better see how the variable obtained
10200 the value in question; or continuing to step @emph{from} the point of the
10201 strange value to see if code motion had simply moved the variable's
10206 In light of such anomalies, a recommended technique is to use @option{-O0}
10207 early in the software development cycle, when extensive debugging capabilities
10208 are most needed, and then move to @option{-O1} and later @option{-O2} as
10209 the debugger becomes less critical.
10210 Whether to use the @option{^-g^/DEBUG^} switch in the release version is
10211 a release management issue.
10213 Note that if you use @option{-g} you can then use the @command{strip} program
10214 on the resulting executable,
10215 which removes both debugging information and global symbols.
10218 @node Inlining of Subprograms
10219 @subsection Inlining of Subprograms
10222 A call to a subprogram in the current unit is inlined if all the
10223 following conditions are met:
10227 The optimization level is at least @option{-O1}.
10230 The called subprogram is suitable for inlining: It must be small enough
10231 and not contain something that @command{gcc} cannot support in inlined
10235 @cindex pragma Inline
10237 Either @code{pragma Inline} applies to the subprogram, or it is local
10238 to the unit and called once from within it, or it is small and automatic
10239 inlining (optimization level @option{-O3}) is specified.
10243 Calls to subprograms in @code{with}'ed units are normally not inlined.
10244 To achieve actual inlining (that is, replacement of the call by the code
10245 in the body of the subprogram), the following conditions must all be true.
10249 The optimization level is at least @option{-O1}.
10252 The called subprogram is suitable for inlining: It must be small enough
10253 and not contain something that @command{gcc} cannot support in inlined
10257 The call appears in a body (not in a package spec).
10260 There is a @code{pragma Inline} for the subprogram.
10263 @cindex @option{-gnatn} (@command{gcc})
10264 The @option{^-gnatn^/INLINE^} switch
10265 is used in the @command{gcc} command line
10268 Even if all these conditions are met, it may not be possible for
10269 the compiler to inline the call, due to the length of the body,
10270 or features in the body that make it impossible for the compiler
10271 to do the inlining.
10273 Note that specifying the @option{-gnatn} switch causes additional
10274 compilation dependencies. Consider the following:
10276 @smallexample @c ada
10296 With the default behavior (no @option{-gnatn} switch specified), the
10297 compilation of the @code{Main} procedure depends only on its own source,
10298 @file{main.adb}, and the spec of the package in file @file{r.ads}. This
10299 means that editing the body of @code{R} does not require recompiling
10302 On the other hand, the call @code{R.Q} is not inlined under these
10303 circumstances. If the @option{-gnatn} switch is present when @code{Main}
10304 is compiled, the call will be inlined if the body of @code{Q} is small
10305 enough, but now @code{Main} depends on the body of @code{R} in
10306 @file{r.adb} as well as on the spec. This means that if this body is edited,
10307 the main program must be recompiled. Note that this extra dependency
10308 occurs whether or not the call is in fact inlined by @command{gcc}.
10310 The use of front end inlining with @option{-gnatN} generates similar
10311 additional dependencies.
10313 @cindex @option{^-fno-inline^/INLINE=SUPPRESS^} (@command{gcc})
10314 Note: The @option{^-fno-inline^/INLINE=SUPPRESS^} switch
10315 can be used to prevent
10316 all inlining. This switch overrides all other conditions and ensures
10317 that no inlining occurs. The extra dependences resulting from
10318 @option{-gnatn} will still be active, even if
10319 this switch is used to suppress the resulting inlining actions.
10321 @cindex @option{-fno-inline-functions} (@command{gcc})
10322 Note: The @option{-fno-inline-functions} switch can be used to prevent
10323 automatic inlining of small subprograms if @option{-O3} is used.
10325 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
10326 Note: The @option{-fno-inline-functions-called-once} switch
10327 can be used to prevent inlining of subprograms local to the unit
10328 and called once from within it if @option{-O1} is used.
10330 Note regarding the use of @option{-O3}: There is no difference in inlining
10331 behavior between @option{-O2} and @option{-O3} for subprograms with an explicit
10332 pragma @code{Inline} assuming the use of @option{-gnatn}
10333 or @option{-gnatN} (the switches that activate inlining). If you have used
10334 pragma @code{Inline} in appropriate cases, then it is usually much better
10335 to use @option{-O2} and @option{-gnatn} and avoid the use of @option{-O3} which
10336 in this case only has the effect of inlining subprograms you did not
10337 think should be inlined. We often find that the use of @option{-O3} slows
10338 down code by performing excessive inlining, leading to increased instruction
10339 cache pressure from the increased code size. So the bottom line here is
10340 that you should not automatically assume that @option{-O3} is better than
10341 @option{-O2}, and indeed you should use @option{-O3} only if tests show that
10342 it actually improves performance.
10344 @node Other Optimization Switches
10345 @subsection Other Optimization Switches
10346 @cindex Optimization Switches
10348 Since @code{GNAT} uses the @command{gcc} back end, all the specialized
10349 @command{gcc} optimization switches are potentially usable. These switches
10350 have not been extensively tested with GNAT but can generally be expected
10351 to work. Examples of switches in this category are
10352 @option{-funroll-loops} and
10353 the various target-specific @option{-m} options (in particular, it has been
10354 observed that @option{-march=pentium4} can significantly improve performance
10355 on appropriate machines). For full details of these switches, see
10356 @ref{Submodel Options,, Hardware Models and Configurations, gcc, Using
10357 the GNU Compiler Collection (GCC)}.
10359 @node Optimization and Strict Aliasing
10360 @subsection Optimization and Strict Aliasing
10362 @cindex Strict Aliasing
10363 @cindex No_Strict_Aliasing
10366 The strong typing capabilities of Ada allow an optimizer to generate
10367 efficient code in situations where other languages would be forced to
10368 make worst case assumptions preventing such optimizations. Consider
10369 the following example:
10371 @smallexample @c ada
10374 type Int1 is new Integer;
10375 type Int2 is new Integer;
10376 type Int1A is access Int1;
10377 type Int2A is access Int2;
10384 for J in Data'Range loop
10385 if Data (J) = Int1V.all then
10386 Int2V.all := Int2V.all + 1;
10395 In this example, since the variable @code{Int1V} can only access objects
10396 of type @code{Int1}, and @code{Int2V} can only access objects of type
10397 @code{Int2}, there is no possibility that the assignment to
10398 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
10399 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
10400 for all iterations of the loop and avoid the extra memory reference
10401 required to dereference it each time through the loop.
10403 This kind of optimization, called strict aliasing analysis, is
10404 triggered by specifying an optimization level of @option{-O2} or
10405 higher or @option{-Os} and allows @code{GNAT} to generate more efficient code
10406 when access values are involved.
10408 However, although this optimization is always correct in terms of
10409 the formal semantics of the Ada Reference Manual, difficulties can
10410 arise if features like @code{Unchecked_Conversion} are used to break
10411 the typing system. Consider the following complete program example:
10413 @smallexample @c ada
10416 type int1 is new integer;
10417 type int2 is new integer;
10418 type a1 is access int1;
10419 type a2 is access int2;
10424 function to_a2 (Input : a1) return a2;
10427 with Unchecked_Conversion;
10429 function to_a2 (Input : a1) return a2 is
10431 new Unchecked_Conversion (a1, a2);
10433 return to_a2u (Input);
10439 with Text_IO; use Text_IO;
10441 v1 : a1 := new int1;
10442 v2 : a2 := to_a2 (v1);
10446 put_line (int1'image (v1.all));
10452 This program prints out 0 in @option{-O0} or @option{-O1}
10453 mode, but it prints out 1 in @option{-O2} mode. That's
10454 because in strict aliasing mode, the compiler can and
10455 does assume that the assignment to @code{v2.all} could not
10456 affect the value of @code{v1.all}, since different types
10459 This behavior is not a case of non-conformance with the standard, since
10460 the Ada RM specifies that an unchecked conversion where the resulting
10461 bit pattern is not a correct value of the target type can result in an
10462 abnormal value and attempting to reference an abnormal value makes the
10463 execution of a program erroneous. That's the case here since the result
10464 does not point to an object of type @code{int2}. This means that the
10465 effect is entirely unpredictable.
10467 However, although that explanation may satisfy a language
10468 lawyer, in practice an applications programmer expects an
10469 unchecked conversion involving pointers to create true
10470 aliases and the behavior of printing 1 seems plain wrong.
10471 In this case, the strict aliasing optimization is unwelcome.
10473 Indeed the compiler recognizes this possibility, and the
10474 unchecked conversion generates a warning:
10477 p2.adb:5:07: warning: possible aliasing problem with type "a2"
10478 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
10479 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
10483 Unfortunately the problem is recognized when compiling the body of
10484 package @code{p2}, but the actual "bad" code is generated while
10485 compiling the body of @code{m} and this latter compilation does not see
10486 the suspicious @code{Unchecked_Conversion}.
10488 As implied by the warning message, there are approaches you can use to
10489 avoid the unwanted strict aliasing optimization in a case like this.
10491 One possibility is to simply avoid the use of @option{-O2}, but
10492 that is a bit drastic, since it throws away a number of useful
10493 optimizations that do not involve strict aliasing assumptions.
10495 A less drastic approach is to compile the program using the
10496 option @option{-fno-strict-aliasing}. Actually it is only the
10497 unit containing the dereferencing of the suspicious pointer
10498 that needs to be compiled. So in this case, if we compile
10499 unit @code{m} with this switch, then we get the expected
10500 value of zero printed. Analyzing which units might need
10501 the switch can be painful, so a more reasonable approach
10502 is to compile the entire program with options @option{-O2}
10503 and @option{-fno-strict-aliasing}. If the performance is
10504 satisfactory with this combination of options, then the
10505 advantage is that the entire issue of possible "wrong"
10506 optimization due to strict aliasing is avoided.
10508 To avoid the use of compiler switches, the configuration
10509 pragma @code{No_Strict_Aliasing} with no parameters may be
10510 used to specify that for all access types, the strict
10511 aliasing optimization should be suppressed.
10513 However, these approaches are still overkill, in that they causes
10514 all manipulations of all access values to be deoptimized. A more
10515 refined approach is to concentrate attention on the specific
10516 access type identified as problematic.
10518 First, if a careful analysis of uses of the pointer shows
10519 that there are no possible problematic references, then
10520 the warning can be suppressed by bracketing the
10521 instantiation of @code{Unchecked_Conversion} to turn
10524 @smallexample @c ada
10525 pragma Warnings (Off);
10527 new Unchecked_Conversion (a1, a2);
10528 pragma Warnings (On);
10532 Of course that approach is not appropriate for this particular
10533 example, since indeed there is a problematic reference. In this
10534 case we can take one of two other approaches.
10536 The first possibility is to move the instantiation of unchecked
10537 conversion to the unit in which the type is declared. In
10538 this example, we would move the instantiation of
10539 @code{Unchecked_Conversion} from the body of package
10540 @code{p2} to the spec of package @code{p1}. Now the
10541 warning disappears. That's because any use of the
10542 access type knows there is a suspicious unchecked
10543 conversion, and the strict aliasing optimization
10544 is automatically suppressed for the type.
10546 If it is not practical to move the unchecked conversion to the same unit
10547 in which the destination access type is declared (perhaps because the
10548 source type is not visible in that unit), you may use pragma
10549 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
10550 same declarative sequence as the declaration of the access type:
10552 @smallexample @c ada
10553 type a2 is access int2;
10554 pragma No_Strict_Aliasing (a2);
10558 Here again, the compiler now knows that the strict aliasing optimization
10559 should be suppressed for any reference to type @code{a2} and the
10560 expected behavior is obtained.
10562 Finally, note that although the compiler can generate warnings for
10563 simple cases of unchecked conversions, there are tricker and more
10564 indirect ways of creating type incorrect aliases which the compiler
10565 cannot detect. Examples are the use of address overlays and unchecked
10566 conversions involving composite types containing access types as
10567 components. In such cases, no warnings are generated, but there can
10568 still be aliasing problems. One safe coding practice is to forbid the
10569 use of address clauses for type overlaying, and to allow unchecked
10570 conversion only for primitive types. This is not really a significant
10571 restriction since any possible desired effect can be achieved by
10572 unchecked conversion of access values.
10574 The aliasing analysis done in strict aliasing mode can certainly
10575 have significant benefits. We have seen cases of large scale
10576 application code where the time is increased by up to 5% by turning
10577 this optimization off. If you have code that includes significant
10578 usage of unchecked conversion, you might want to just stick with
10579 @option{-O1} and avoid the entire issue. If you get adequate
10580 performance at this level of optimization level, that's probably
10581 the safest approach. If tests show that you really need higher
10582 levels of optimization, then you can experiment with @option{-O2}
10583 and @option{-O2 -fno-strict-aliasing} to see how much effect this
10584 has on size and speed of the code. If you really need to use
10585 @option{-O2} with strict aliasing in effect, then you should
10586 review any uses of unchecked conversion of access types,
10587 particularly if you are getting the warnings described above.
10590 @node Coverage Analysis
10591 @subsection Coverage Analysis
10594 GNAT supports the HP Performance Coverage Analyzer (PCA), which allows
10595 the user to determine the distribution of execution time across a program,
10596 @pxref{Profiling} for details of usage.
10600 @node Text_IO Suggestions
10601 @section @code{Text_IO} Suggestions
10602 @cindex @code{Text_IO} and performance
10605 The @code{Ada.Text_IO} package has fairly high overheads due in part to
10606 the requirement of maintaining page and line counts. If performance
10607 is critical, a recommendation is to use @code{Stream_IO} instead of
10608 @code{Text_IO} for volume output, since this package has less overhead.
10610 If @code{Text_IO} must be used, note that by default output to the standard
10611 output and standard error files is unbuffered (this provides better
10612 behavior when output statements are used for debugging, or if the
10613 progress of a program is observed by tracking the output, e.g. by
10614 using the Unix @command{tail -f} command to watch redirected output.
10616 If you are generating large volumes of output with @code{Text_IO} and
10617 performance is an important factor, use a designated file instead
10618 of the standard output file, or change the standard output file to
10619 be buffered using @code{Interfaces.C_Streams.setvbuf}.
10623 @node Reducing Size of Ada Executables with gnatelim
10624 @section Reducing Size of Ada Executables with @code{gnatelim}
10628 This section describes @command{gnatelim}, a tool which detects unused
10629 subprograms and helps the compiler to create a smaller executable for your
10634 * Running gnatelim::
10635 * Correcting the List of Eliminate Pragmas::
10636 * Making Your Executables Smaller::
10637 * Summary of the gnatelim Usage Cycle::
10640 @node About gnatelim
10641 @subsection About @code{gnatelim}
10644 When a program shares a set of Ada
10645 packages with other programs, it may happen that this program uses
10646 only a fraction of the subprograms defined in these packages. The code
10647 created for these unused subprograms increases the size of the executable.
10649 @code{gnatelim} tracks unused subprograms in an Ada program and
10650 outputs a list of GNAT-specific pragmas @code{Eliminate} marking all the
10651 subprograms that are declared but never called. By placing the list of
10652 @code{Eliminate} pragmas in the GNAT configuration file @file{gnat.adc} and
10653 recompiling your program, you may decrease the size of its executable,
10654 because the compiler will not generate the code for 'eliminated' subprograms.
10655 @xref{Pragma Eliminate,,, gnat_rm, GNAT Reference Manual}, for more
10656 information about this pragma.
10658 @code{gnatelim} needs as its input data the name of the main subprogram
10659 and a bind file for a main subprogram.
10661 To create a bind file for @code{gnatelim}, run @code{gnatbind} for
10662 the main subprogram. @code{gnatelim} can work with both Ada and C
10663 bind files; when both are present, it uses the Ada bind file.
10664 The following commands will build the program and create the bind file:
10667 $ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
10668 $ gnatbind main_prog
10671 Note that @code{gnatelim} needs neither object nor ALI files.
10673 @node Running gnatelim
10674 @subsection Running @code{gnatelim}
10677 @code{gnatelim} has the following command-line interface:
10680 $ gnatelim @ovar{options} name
10684 @code{name} should be a name of a source file that contains the main subprogram
10685 of a program (partition).
10687 @code{gnatelim} has the following switches:
10692 @cindex @option{^-q^/QUIET^} (@command{gnatelim})
10693 Quiet mode: by default @code{gnatelim} outputs to the standard error
10694 stream the number of program units left to be processed. This option turns
10697 @item ^-v^/VERBOSE^
10698 @cindex @option{^-v^/VERBOSE^} (@command{gnatelim})
10699 Verbose mode: @code{gnatelim} version information is printed as Ada
10700 comments to the standard output stream. Also, in addition to the number of
10701 program units left @code{gnatelim} will output the name of the current unit
10705 @cindex @option{^-a^/ALL^} (@command{gnatelim})
10706 Also look for subprograms from the GNAT run time that can be eliminated. Note
10707 that when @file{gnat.adc} is produced using this switch, the entire program
10708 must be recompiled with switch @option{^-a^/ALL_FILES^} to @command{gnatmake}.
10710 @item ^-I^/INCLUDE_DIRS=^@var{dir}
10711 @cindex @option{^-I^/INCLUDE_DIRS^} (@command{gnatelim})
10712 When looking for source files also look in directory @var{dir}. Specifying
10713 @option{^-I-^/INCLUDE_DIRS=-^} instructs @code{gnatelim} not to look for
10714 sources in the current directory.
10716 @item ^-b^/BIND_FILE=^@var{bind_file}
10717 @cindex @option{^-b^/BIND_FILE^} (@command{gnatelim})
10718 Specifies @var{bind_file} as the bind file to process. If not set, the name
10719 of the bind file is computed from the full expanded Ada name
10720 of a main subprogram.
10722 @item ^-C^/CONFIG_FILE=^@var{config_file}
10723 @cindex @option{^-C^/CONFIG_FILE^} (@command{gnatelim})
10724 Specifies a file @var{config_file} that contains configuration pragmas. The
10725 file must be specified with full path.
10727 @item ^--GCC^/COMPILER^=@var{compiler_name}
10728 @cindex @option{^-GCC^/COMPILER^} (@command{gnatelim})
10729 Instructs @code{gnatelim} to use specific @command{gcc} compiler instead of one
10730 available on the path.
10732 @item ^--GNATMAKE^/GNATMAKE^=@var{gnatmake_name}
10733 @cindex @option{^--GNATMAKE^/GNATMAKE^} (@command{gnatelim})
10734 Instructs @code{gnatelim} to use specific @command{gnatmake} instead of one
10735 available on the path.
10739 @code{gnatelim} sends its output to the standard output stream, and all the
10740 tracing and debug information is sent to the standard error stream.
10741 In order to produce a proper GNAT configuration file
10742 @file{gnat.adc}, redirection must be used:
10746 $ PIPE GNAT ELIM MAIN_PROG.ADB > GNAT.ADC
10749 $ gnatelim main_prog.adb > gnat.adc
10758 $ gnatelim main_prog.adb >> gnat.adc
10762 in order to append the @code{gnatelim} output to the existing contents of
10766 @node Correcting the List of Eliminate Pragmas
10767 @subsection Correcting the List of Eliminate Pragmas
10770 In some rare cases @code{gnatelim} may try to eliminate
10771 subprograms that are actually called in the program. In this case, the
10772 compiler will generate an error message of the form:
10775 file.adb:106:07: cannot call eliminated subprogram "My_Prog"
10779 You will need to manually remove the wrong @code{Eliminate} pragmas from
10780 the @file{gnat.adc} file. You should recompile your program
10781 from scratch after that, because you need a consistent @file{gnat.adc} file
10782 during the entire compilation.
10784 @node Making Your Executables Smaller
10785 @subsection Making Your Executables Smaller
10788 In order to get a smaller executable for your program you now have to
10789 recompile the program completely with the new @file{gnat.adc} file
10790 created by @code{gnatelim} in your current directory:
10793 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10797 (Use the @option{^-f^/FORCE_COMPILE^} option for @command{gnatmake} to
10798 recompile everything
10799 with the set of pragmas @code{Eliminate} that you have obtained with
10800 @command{gnatelim}).
10802 Be aware that the set of @code{Eliminate} pragmas is specific to each
10803 program. It is not recommended to merge sets of @code{Eliminate}
10804 pragmas created for different programs in one @file{gnat.adc} file.
10806 @node Summary of the gnatelim Usage Cycle
10807 @subsection Summary of the gnatelim Usage Cycle
10810 Here is a quick summary of the steps to be taken in order to reduce
10811 the size of your executables with @code{gnatelim}. You may use
10812 other GNAT options to control the optimization level,
10813 to produce the debugging information, to set search path, etc.
10817 Produce a bind file
10820 $ gnatmake ^-c main_prog^/ACTIONS=COMPILE MAIN_PROG^
10821 $ gnatbind main_prog
10825 Generate a list of @code{Eliminate} pragmas
10828 $ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
10831 $ gnatelim main_prog >@r{[}>@r{]} gnat.adc
10836 Recompile the application
10839 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10844 @node Reducing Size of Executables with unused subprogram/data elimination
10845 @section Reducing Size of Executables with Unused Subprogram/Data Elimination
10846 @findex unused subprogram/data elimination
10849 This section describes how you can eliminate unused subprograms and data from
10850 your executable just by setting options at compilation time.
10853 * About unused subprogram/data elimination::
10854 * Compilation options::
10855 * Example of unused subprogram/data elimination::
10858 @node About unused subprogram/data elimination
10859 @subsection About unused subprogram/data elimination
10862 By default, an executable contains all code and data of its composing objects
10863 (directly linked or coming from statically linked libraries), even data or code
10864 never used by this executable.
10866 This feature will allow you to eliminate such unused code from your
10867 executable, making it smaller (in disk and in memory).
10869 This functionality is available on all Linux platforms except for the IA-64
10870 architecture and on all cross platforms using the ELF binary file format.
10871 In both cases GNU binutils version 2.16 or later are required to enable it.
10873 @node Compilation options
10874 @subsection Compilation options
10877 The operation of eliminating the unused code and data from the final executable
10878 is directly performed by the linker.
10880 In order to do this, it has to work with objects compiled with the
10882 @option{-ffunction-sections} @option{-fdata-sections}.
10883 @cindex @option{-ffunction-sections} (@command{gcc})
10884 @cindex @option{-fdata-sections} (@command{gcc})
10885 These options are usable with C and Ada files.
10886 They will place respectively each
10887 function or data in a separate section in the resulting object file.
10889 Once the objects and static libraries are created with these options, the
10890 linker can perform the dead code elimination. You can do this by setting
10891 the @option{-Wl,--gc-sections} option to gcc command or in the
10892 @option{-largs} section of @command{gnatmake}. This will perform a
10893 garbage collection of code and data never referenced.
10895 If the linker performs a partial link (@option{-r} ld linker option), then you
10896 will need to provide one or several entry point using the
10897 @option{-e} / @option{--entry} ld option.
10899 Note that objects compiled without the @option{-ffunction-sections} and
10900 @option{-fdata-sections} options can still be linked with the executable.
10901 However, no dead code elimination will be performed on those objects (they will
10904 The GNAT static library is now compiled with -ffunction-sections and
10905 -fdata-sections on some platforms. This allows you to eliminate the unused code
10906 and data of the GNAT library from your executable.
10908 @node Example of unused subprogram/data elimination
10909 @subsection Example of unused subprogram/data elimination
10912 Here is a simple example:
10914 @smallexample @c ada
10923 Used_Data : Integer;
10924 Unused_Data : Integer;
10926 procedure Used (Data : Integer);
10927 procedure Unused (Data : Integer);
10930 package body Aux is
10931 procedure Used (Data : Integer) is
10936 procedure Unused (Data : Integer) is
10938 Unused_Data := Data;
10944 @code{Unused} and @code{Unused_Data} are never referenced in this code
10945 excerpt, and hence they may be safely removed from the final executable.
10950 $ nm test | grep used
10951 020015f0 T aux__unused
10952 02005d88 B aux__unused_data
10953 020015cc T aux__used
10954 02005d84 B aux__used_data
10956 $ gnatmake test -cargs -fdata-sections -ffunction-sections \
10957 -largs -Wl,--gc-sections
10959 $ nm test | grep used
10960 02005350 T aux__used
10961 0201ffe0 B aux__used_data
10965 It can be observed that the procedure @code{Unused} and the object
10966 @code{Unused_Data} are removed by the linker when using the
10967 appropriate options.
10969 @c ********************************
10970 @node Renaming Files Using gnatchop
10971 @chapter Renaming Files Using @code{gnatchop}
10975 This chapter discusses how to handle files with multiple units by using
10976 the @code{gnatchop} utility. This utility is also useful in renaming
10977 files to meet the standard GNAT default file naming conventions.
10980 * Handling Files with Multiple Units::
10981 * Operating gnatchop in Compilation Mode::
10982 * Command Line for gnatchop::
10983 * Switches for gnatchop::
10984 * Examples of gnatchop Usage::
10987 @node Handling Files with Multiple Units
10988 @section Handling Files with Multiple Units
10991 The basic compilation model of GNAT requires that a file submitted to the
10992 compiler have only one unit and there be a strict correspondence
10993 between the file name and the unit name.
10995 The @code{gnatchop} utility allows both of these rules to be relaxed,
10996 allowing GNAT to process files which contain multiple compilation units
10997 and files with arbitrary file names. @code{gnatchop}
10998 reads the specified file and generates one or more output files,
10999 containing one unit per file. The unit and the file name correspond,
11000 as required by GNAT.
11002 If you want to permanently restructure a set of ``foreign'' files so that
11003 they match the GNAT rules, and do the remaining development using the
11004 GNAT structure, you can simply use @command{gnatchop} once, generate the
11005 new set of files and work with them from that point on.
11007 Alternatively, if you want to keep your files in the ``foreign'' format,
11008 perhaps to maintain compatibility with some other Ada compilation
11009 system, you can set up a procedure where you use @command{gnatchop} each
11010 time you compile, regarding the source files that it writes as temporary
11011 files that you throw away.
11013 Note that if your file containing multiple units starts with a byte order
11014 mark (BOM) specifying UTF-8 encoding, then the files generated by gnatchop
11015 will each start with a copy of this BOM, meaning that they can be compiled
11016 automatically in UTF-8 mode without needing to specify an explicit encoding.
11018 @node Operating gnatchop in Compilation Mode
11019 @section Operating gnatchop in Compilation Mode
11022 The basic function of @code{gnatchop} is to take a file with multiple units
11023 and split it into separate files. The boundary between files is reasonably
11024 clear, except for the issue of comments and pragmas. In default mode, the
11025 rule is that any pragmas between units belong to the previous unit, except
11026 that configuration pragmas always belong to the following unit. Any comments
11027 belong to the following unit. These rules
11028 almost always result in the right choice of
11029 the split point without needing to mark it explicitly and most users will
11030 find this default to be what they want. In this default mode it is incorrect to
11031 submit a file containing only configuration pragmas, or one that ends in
11032 configuration pragmas, to @code{gnatchop}.
11034 However, using a special option to activate ``compilation mode'',
11036 can perform another function, which is to provide exactly the semantics
11037 required by the RM for handling of configuration pragmas in a compilation.
11038 In the absence of configuration pragmas (at the main file level), this
11039 option has no effect, but it causes such configuration pragmas to be handled
11040 in a quite different manner.
11042 First, in compilation mode, if @code{gnatchop} is given a file that consists of
11043 only configuration pragmas, then this file is appended to the
11044 @file{gnat.adc} file in the current directory. This behavior provides
11045 the required behavior described in the RM for the actions to be taken
11046 on submitting such a file to the compiler, namely that these pragmas
11047 should apply to all subsequent compilations in the same compilation
11048 environment. Using GNAT, the current directory, possibly containing a
11049 @file{gnat.adc} file is the representation
11050 of a compilation environment. For more information on the
11051 @file{gnat.adc} file, see @ref{Handling of Configuration Pragmas}.
11053 Second, in compilation mode, if @code{gnatchop}
11054 is given a file that starts with
11055 configuration pragmas, and contains one or more units, then these
11056 configuration pragmas are prepended to each of the chopped files. This
11057 behavior provides the required behavior described in the RM for the
11058 actions to be taken on compiling such a file, namely that the pragmas
11059 apply to all units in the compilation, but not to subsequently compiled
11062 Finally, if configuration pragmas appear between units, they are appended
11063 to the previous unit. This results in the previous unit being illegal,
11064 since the compiler does not accept configuration pragmas that follow
11065 a unit. This provides the required RM behavior that forbids configuration
11066 pragmas other than those preceding the first compilation unit of a
11069 For most purposes, @code{gnatchop} will be used in default mode. The
11070 compilation mode described above is used only if you need exactly
11071 accurate behavior with respect to compilations, and you have files
11072 that contain multiple units and configuration pragmas. In this
11073 circumstance the use of @code{gnatchop} with the compilation mode
11074 switch provides the required behavior, and is for example the mode
11075 in which GNAT processes the ACVC tests.
11077 @node Command Line for gnatchop
11078 @section Command Line for @code{gnatchop}
11081 The @code{gnatchop} command has the form:
11084 $ gnatchop switches @var{file name} @r{[}@var{file name} @dots{}@r{]}
11089 The only required argument is the file name of the file to be chopped.
11090 There are no restrictions on the form of this file name. The file itself
11091 contains one or more Ada units, in normal GNAT format, concatenated
11092 together. As shown, more than one file may be presented to be chopped.
11094 When run in default mode, @code{gnatchop} generates one output file in
11095 the current directory for each unit in each of the files.
11097 @var{directory}, if specified, gives the name of the directory to which
11098 the output files will be written. If it is not specified, all files are
11099 written to the current directory.
11101 For example, given a
11102 file called @file{hellofiles} containing
11104 @smallexample @c ada
11109 with Text_IO; use Text_IO;
11112 Put_Line ("Hello");
11122 $ gnatchop ^hellofiles^HELLOFILES.^
11126 generates two files in the current directory, one called
11127 @file{hello.ads} containing the single line that is the procedure spec,
11128 and the other called @file{hello.adb} containing the remaining text. The
11129 original file is not affected. The generated files can be compiled in
11133 When gnatchop is invoked on a file that is empty or that contains only empty
11134 lines and/or comments, gnatchop will not fail, but will not produce any
11137 For example, given a
11138 file called @file{toto.txt} containing
11140 @smallexample @c ada
11152 $ gnatchop ^toto.txt^TOT.TXT^
11156 will not produce any new file and will result in the following warnings:
11159 toto.txt:1:01: warning: empty file, contains no compilation units
11160 no compilation units found
11161 no source files written
11164 @node Switches for gnatchop
11165 @section Switches for @code{gnatchop}
11168 @command{gnatchop} recognizes the following switches:
11174 @cindex @option{--version} @command{gnatchop}
11175 Display Copyright and version, then exit disregarding all other options.
11178 @cindex @option{--help} @command{gnatchop}
11179 If @option{--version} was not used, display usage, then exit disregarding
11182 @item ^-c^/COMPILATION^
11183 @cindex @option{^-c^/COMPILATION^} (@code{gnatchop})
11184 Causes @code{gnatchop} to operate in compilation mode, in which
11185 configuration pragmas are handled according to strict RM rules. See
11186 previous section for a full description of this mode.
11189 @item -gnat@var{xxx}
11190 This passes the given @option{-gnat@var{xxx}} switch to @code{gnat} which is
11191 used to parse the given file. Not all @var{xxx} options make sense,
11192 but for example, the use of @option{-gnati2} allows @code{gnatchop} to
11193 process a source file that uses Latin-2 coding for identifiers.
11197 Causes @code{gnatchop} to generate a brief help summary to the standard
11198 output file showing usage information.
11200 @item ^-k@var{mm}^/FILE_NAME_MAX_LENGTH=@var{mm}^
11201 @cindex @option{^-k^/FILE_NAME_MAX_LENGTH^} (@code{gnatchop})
11202 Limit generated file names to the specified number @code{mm}
11204 This is useful if the
11205 resulting set of files is required to be interoperable with systems
11206 which limit the length of file names.
11208 If no value is given, or
11209 if no @code{/FILE_NAME_MAX_LENGTH} qualifier is given,
11210 a default of 39, suitable for OpenVMS Alpha
11211 Systems, is assumed
11214 No space is allowed between the @option{-k} and the numeric value. The numeric
11215 value may be omitted in which case a default of @option{-k8},
11217 with DOS-like file systems, is used. If no @option{-k} switch
11219 there is no limit on the length of file names.
11222 @item ^-p^/PRESERVE^
11223 @cindex @option{^-p^/PRESERVE^} (@code{gnatchop})
11224 Causes the file ^modification^creation^ time stamp of the input file to be
11225 preserved and used for the time stamp of the output file(s). This may be
11226 useful for preserving coherency of time stamps in an environment where
11227 @code{gnatchop} is used as part of a standard build process.
11230 @cindex @option{^-q^/QUIET^} (@code{gnatchop})
11231 Causes output of informational messages indicating the set of generated
11232 files to be suppressed. Warnings and error messages are unaffected.
11234 @item ^-r^/REFERENCE^
11235 @cindex @option{^-r^/REFERENCE^} (@code{gnatchop})
11236 @findex Source_Reference
11237 Generate @code{Source_Reference} pragmas. Use this switch if the output
11238 files are regarded as temporary and development is to be done in terms
11239 of the original unchopped file. This switch causes
11240 @code{Source_Reference} pragmas to be inserted into each of the
11241 generated files to refers back to the original file name and line number.
11242 The result is that all error messages refer back to the original
11244 In addition, the debugging information placed into the object file (when
11245 the @option{^-g^/DEBUG^} switch of @command{gcc} or @command{gnatmake} is
11247 also refers back to this original file so that tools like profilers and
11248 debuggers will give information in terms of the original unchopped file.
11250 If the original file to be chopped itself contains
11251 a @code{Source_Reference}
11252 pragma referencing a third file, then gnatchop respects
11253 this pragma, and the generated @code{Source_Reference} pragmas
11254 in the chopped file refer to the original file, with appropriate
11255 line numbers. This is particularly useful when @code{gnatchop}
11256 is used in conjunction with @code{gnatprep} to compile files that
11257 contain preprocessing statements and multiple units.
11259 @item ^-v^/VERBOSE^
11260 @cindex @option{^-v^/VERBOSE^} (@code{gnatchop})
11261 Causes @code{gnatchop} to operate in verbose mode. The version
11262 number and copyright notice are output, as well as exact copies of
11263 the gnat1 commands spawned to obtain the chop control information.
11265 @item ^-w^/OVERWRITE^
11266 @cindex @option{^-w^/OVERWRITE^} (@code{gnatchop})
11267 Overwrite existing file names. Normally @code{gnatchop} regards it as a
11268 fatal error if there is already a file with the same name as a
11269 file it would otherwise output, in other words if the files to be
11270 chopped contain duplicated units. This switch bypasses this
11271 check, and causes all but the last instance of such duplicated
11272 units to be skipped.
11275 @item --GCC=@var{xxxx}
11276 @cindex @option{--GCC=} (@code{gnatchop})
11277 Specify the path of the GNAT parser to be used. When this switch is used,
11278 no attempt is made to add the prefix to the GNAT parser executable.
11282 @node Examples of gnatchop Usage
11283 @section Examples of @code{gnatchop} Usage
11287 @item gnatchop /OVERWRITE HELLO_S.ADA [PRERELEASE.FILES]
11290 @item gnatchop -w hello_s.ada prerelease/files
11293 Chops the source file @file{hello_s.ada}. The output files will be
11294 placed in the directory @file{^prerelease/files^[PRERELEASE.FILES]^},
11296 files with matching names in that directory (no files in the current
11297 directory are modified).
11299 @item gnatchop ^archive^ARCHIVE.^
11300 Chops the source file @file{^archive^ARCHIVE.^}
11301 into the current directory. One
11302 useful application of @code{gnatchop} is in sending sets of sources
11303 around, for example in email messages. The required sources are simply
11304 concatenated (for example, using a ^Unix @code{cat}^VMS @code{APPEND/NEW}^
11306 @command{gnatchop} is used at the other end to reconstitute the original
11309 @item gnatchop file1 file2 file3 direc
11310 Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing
11311 the resulting files in the directory @file{direc}. Note that if any units
11312 occur more than once anywhere within this set of files, an error message
11313 is generated, and no files are written. To override this check, use the
11314 @option{^-w^/OVERWRITE^} switch,
11315 in which case the last occurrence in the last file will
11316 be the one that is output, and earlier duplicate occurrences for a given
11317 unit will be skipped.
11320 @node Configuration Pragmas
11321 @chapter Configuration Pragmas
11322 @cindex Configuration pragmas
11323 @cindex Pragmas, configuration
11326 Configuration pragmas include those pragmas described as
11327 such in the Ada Reference Manual, as well as
11328 implementation-dependent pragmas that are configuration pragmas.
11329 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
11330 for details on these additional GNAT-specific configuration pragmas.
11331 Most notably, the pragma @code{Source_File_Name}, which allows
11332 specifying non-default names for source files, is a configuration
11333 pragma. The following is a complete list of configuration pragmas
11334 recognized by GNAT:
11342 Assume_No_Invalid_Values
11347 Compile_Time_Warning
11349 Component_Alignment
11350 Convention_Identifier
11358 External_Name_Casing
11361 Float_Representation
11374 Priority_Specific_Dispatching
11377 Propagate_Exceptions
11380 Restricted_Run_Time
11382 Restrictions_Warnings
11385 Source_File_Name_Project
11388 Suppress_Exception_Locations
11389 Task_Dispatching_Policy
11395 Wide_Character_Encoding
11400 * Handling of Configuration Pragmas::
11401 * The Configuration Pragmas Files::
11404 @node Handling of Configuration Pragmas
11405 @section Handling of Configuration Pragmas
11407 Configuration pragmas may either appear at the start of a compilation
11408 unit, in which case they apply only to that unit, or they may apply to
11409 all compilations performed in a given compilation environment.
11411 GNAT also provides the @code{gnatchop} utility to provide an automatic
11412 way to handle configuration pragmas following the semantics for
11413 compilations (that is, files with multiple units), described in the RM.
11414 See @ref{Operating gnatchop in Compilation Mode} for details.
11415 However, for most purposes, it will be more convenient to edit the
11416 @file{gnat.adc} file that contains configuration pragmas directly,
11417 as described in the following section.
11419 @node The Configuration Pragmas Files
11420 @section The Configuration Pragmas Files
11421 @cindex @file{gnat.adc}
11424 In GNAT a compilation environment is defined by the current
11425 directory at the time that a compile command is given. This current
11426 directory is searched for a file whose name is @file{gnat.adc}. If
11427 this file is present, it is expected to contain one or more
11428 configuration pragmas that will be applied to the current compilation.
11429 However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not
11432 Configuration pragmas may be entered into the @file{gnat.adc} file
11433 either by running @code{gnatchop} on a source file that consists only of
11434 configuration pragmas, or more conveniently by
11435 direct editing of the @file{gnat.adc} file, which is a standard format
11438 In addition to @file{gnat.adc}, additional files containing configuration
11439 pragmas may be applied to the current compilation using the switch
11440 @option{-gnatec}@var{path}. @var{path} must designate an existing file that
11441 contains only configuration pragmas. These configuration pragmas are
11442 in addition to those found in @file{gnat.adc} (provided @file{gnat.adc}
11443 is present and switch @option{-gnatA} is not used).
11445 It is allowed to specify several switches @option{-gnatec}, all of which
11446 will be taken into account.
11448 If you are using project file, a separate mechanism is provided using
11449 project attributes, see @ref{Specifying Configuration Pragmas} for more
11453 Of special interest to GNAT OpenVMS Alpha is the following
11454 configuration pragma:
11456 @smallexample @c ada
11458 pragma Extend_System (Aux_DEC);
11463 In the presence of this pragma, GNAT adds to the definition of the
11464 predefined package SYSTEM all the additional types and subprograms that are
11465 defined in HP Ada. See @ref{Compatibility with HP Ada} for details.
11468 @node Handling Arbitrary File Naming Conventions Using gnatname
11469 @chapter Handling Arbitrary File Naming Conventions Using @code{gnatname}
11470 @cindex Arbitrary File Naming Conventions
11473 * Arbitrary File Naming Conventions::
11474 * Running gnatname::
11475 * Switches for gnatname::
11476 * Examples of gnatname Usage::
11479 @node Arbitrary File Naming Conventions
11480 @section Arbitrary File Naming Conventions
11483 The GNAT compiler must be able to know the source file name of a compilation
11484 unit. When using the standard GNAT default file naming conventions
11485 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
11486 does not need additional information.
11489 When the source file names do not follow the standard GNAT default file naming
11490 conventions, the GNAT compiler must be given additional information through
11491 a configuration pragmas file (@pxref{Configuration Pragmas})
11493 When the non-standard file naming conventions are well-defined,
11494 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
11495 (@pxref{Alternative File Naming Schemes}) may be sufficient. However,
11496 if the file naming conventions are irregular or arbitrary, a number
11497 of pragma @code{Source_File_Name} for individual compilation units
11499 To help maintain the correspondence between compilation unit names and
11500 source file names within the compiler,
11501 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
11504 @node Running gnatname
11505 @section Running @code{gnatname}
11508 The usual form of the @code{gnatname} command is
11511 $ gnatname @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}
11512 @r{[}--and @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}@r{]}
11516 All of the arguments are optional. If invoked without any argument,
11517 @code{gnatname} will display its usage.
11520 When used with at least one naming pattern, @code{gnatname} will attempt to
11521 find all the compilation units in files that follow at least one of the
11522 naming patterns. To find these compilation units,
11523 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
11527 One or several Naming Patterns may be given as arguments to @code{gnatname}.
11528 Each Naming Pattern is enclosed between double quotes.
11529 A Naming Pattern is a regular expression similar to the wildcard patterns
11530 used in file names by the Unix shells or the DOS prompt.
11533 @code{gnatname} may be called with several sections of directories/patterns.
11534 Sections are separated by switch @code{--and}. In each section, there must be
11535 at least one pattern. If no directory is specified in a section, the current
11536 directory (or the project directory is @code{-P} is used) is implied.
11537 The options other that the directory switches and the patterns apply globally
11538 even if they are in different sections.
11541 Examples of Naming Patterns are
11550 For a more complete description of the syntax of Naming Patterns,
11551 see the second kind of regular expressions described in @file{g-regexp.ads}
11552 (the ``Glob'' regular expressions).
11555 When invoked with no switch @code{-P}, @code{gnatname} will create a
11556 configuration pragmas file @file{gnat.adc} in the current working directory,
11557 with pragmas @code{Source_File_Name} for each file that contains a valid Ada
11560 @node Switches for gnatname
11561 @section Switches for @code{gnatname}
11564 Switches for @code{gnatname} must precede any specified Naming Pattern.
11567 You may specify any of the following switches to @code{gnatname}:
11573 @cindex @option{--version} @command{gnatname}
11574 Display Copyright and version, then exit disregarding all other options.
11577 @cindex @option{--help} @command{gnatname}
11578 If @option{--version} was not used, display usage, then exit disregarding
11582 Start another section of directories/patterns.
11584 @item ^-c^/CONFIG_FILE=^@file{file}
11585 @cindex @option{^-c^/CONFIG_FILE^} (@code{gnatname})
11586 Create a configuration pragmas file @file{file} (instead of the default
11589 There may be zero, one or more space between @option{-c} and
11592 @file{file} may include directory information. @file{file} must be
11593 writable. There may be only one switch @option{^-c^/CONFIG_FILE^}.
11594 When a switch @option{^-c^/CONFIG_FILE^} is
11595 specified, no switch @option{^-P^/PROJECT_FILE^} may be specified (see below).
11597 @item ^-d^/SOURCE_DIRS=^@file{dir}
11598 @cindex @option{^-d^/SOURCE_DIRS^} (@code{gnatname})
11599 Look for source files in directory @file{dir}. There may be zero, one or more
11600 spaces between @option{^-d^/SOURCE_DIRS=^} and @file{dir}.
11601 When a switch @option{^-d^/SOURCE_DIRS^}
11602 is specified, the current working directory will not be searched for source
11603 files, unless it is explicitly specified with a @option{^-d^/SOURCE_DIRS^}
11604 or @option{^-D^/DIR_FILES^} switch.
11605 Several switches @option{^-d^/SOURCE_DIRS^} may be specified.
11606 If @file{dir} is a relative path, it is relative to the directory of
11607 the configuration pragmas file specified with switch
11608 @option{^-c^/CONFIG_FILE^},
11609 or to the directory of the project file specified with switch
11610 @option{^-P^/PROJECT_FILE^} or,
11611 if neither switch @option{^-c^/CONFIG_FILE^}
11612 nor switch @option{^-P^/PROJECT_FILE^} are specified, it is relative to the
11613 current working directory. The directory
11614 specified with switch @option{^-d^/SOURCE_DIRS^} must exist and be readable.
11616 @item ^-D^/DIRS_FILE=^@file{file}
11617 @cindex @option{^-D^/DIRS_FILE^} (@code{gnatname})
11618 Look for source files in all directories listed in text file @file{file}.
11619 There may be zero, one or more spaces between @option{^-D^/DIRS_FILE=^}
11621 @file{file} must be an existing, readable text file.
11622 Each nonempty line in @file{file} must be a directory.
11623 Specifying switch @option{^-D^/DIRS_FILE^} is equivalent to specifying as many
11624 switches @option{^-d^/SOURCE_DIRS^} as there are nonempty lines in
11627 @item ^-f^/FOREIGN_PATTERN=^@file{pattern}
11628 @cindex @option{^-f^/FOREIGN_PATTERN^} (@code{gnatname})
11629 Foreign patterns. Using this switch, it is possible to add sources of languages
11630 other than Ada to the list of sources of a project file.
11631 It is only useful if a ^-P^/PROJECT_FILE^ switch is used.
11634 gnatname ^-Pprj -f"*.c"^/PROJECT_FILE=PRJ /FOREIGN_PATTERN=*.C^ "*.ada"
11637 will look for Ada units in all files with the @file{.ada} extension,
11638 and will add to the list of file for project @file{prj.gpr} the C files
11639 with extension @file{.^c^C^}.
11642 @cindex @option{^-h^/HELP^} (@code{gnatname})
11643 Output usage (help) information. The output is written to @file{stdout}.
11645 @item ^-P^/PROJECT_FILE=^@file{proj}
11646 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatname})
11647 Create or update project file @file{proj}. There may be zero, one or more space
11648 between @option{-P} and @file{proj}. @file{proj} may include directory
11649 information. @file{proj} must be writable.
11650 There may be only one switch @option{^-P^/PROJECT_FILE^}.
11651 When a switch @option{^-P^/PROJECT_FILE^} is specified,
11652 no switch @option{^-c^/CONFIG_FILE^} may be specified.
11654 @item ^-v^/VERBOSE^
11655 @cindex @option{^-v^/VERBOSE^} (@code{gnatname})
11656 Verbose mode. Output detailed explanation of behavior to @file{stdout}.
11657 This includes name of the file written, the name of the directories to search
11658 and, for each file in those directories whose name matches at least one of
11659 the Naming Patterns, an indication of whether the file contains a unit,
11660 and if so the name of the unit.
11662 @item ^-v -v^/VERBOSE /VERBOSE^
11663 @cindex @option{^-v -v^/VERBOSE /VERBOSE^} (@code{gnatname})
11664 Very Verbose mode. In addition to the output produced in verbose mode,
11665 for each file in the searched directories whose name matches none of
11666 the Naming Patterns, an indication is given that there is no match.
11668 @item ^-x^/EXCLUDED_PATTERN=^@file{pattern}
11669 @cindex @option{^-x^/EXCLUDED_PATTERN^} (@code{gnatname})
11670 Excluded patterns. Using this switch, it is possible to exclude some files
11671 that would match the name patterns. For example,
11673 gnatname ^-x "*_nt.ada"^/EXCLUDED_PATTERN=*_nt.ada^ "*.ada"
11676 will look for Ada units in all files with the @file{.ada} extension,
11677 except those whose names end with @file{_nt.ada}.
11681 @node Examples of gnatname Usage
11682 @section Examples of @code{gnatname} Usage
11686 $ gnatname /CONFIG_FILE=[HOME.ME]NAMES.ADC /SOURCE_DIRS=SOURCES "[a-z]*.ada*"
11692 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
11697 In this example, the directory @file{^/home/me^[HOME.ME]^} must already exist
11698 and be writable. In addition, the directory
11699 @file{^/home/me/sources^[HOME.ME.SOURCES]^} (specified by
11700 @option{^-d sources^/SOURCE_DIRS=SOURCES^}) must exist and be readable.
11703 Note the optional spaces after @option{-c} and @option{-d}.
11708 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
11709 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
11712 $ gnatname /PROJECT_FILE=[HOME.ME]PROJ
11713 /EXCLUDED_PATTERN=*_nt_body.ada
11714 /SOURCE_DIRS=(SOURCES,[SOURCES.PLUS])
11715 /DIRS_FILE=COMMON_DIRS.TXT "body_*" "spec_*"
11719 Note that several switches @option{^-d^/SOURCE_DIRS^} may be used,
11720 even in conjunction with one or several switches
11721 @option{^-D^/DIRS_FILE^}. Several Naming Patterns and one excluded pattern
11722 are used in this example.
11724 @c *****************************************
11725 @c * G N A T P r o j e c t M a n a g e r *
11726 @c *****************************************
11727 @node GNAT Project Manager
11728 @chapter GNAT Project Manager
11732 * Examples of Project Files::
11733 * Project File Syntax::
11734 * Objects and Sources in Project Files::
11735 * Importing Projects::
11736 * Project Extension::
11737 * Project Hierarchy Extension::
11738 * External References in Project Files::
11739 * Packages in Project Files::
11740 * Variables from Imported Projects::
11742 * Library Projects::
11743 * Stand-alone Library Projects::
11744 * Switches Related to Project Files::
11745 * Tools Supporting Project Files::
11746 * An Extended Example::
11747 * Project File Complete Syntax::
11750 @c ****************
11751 @c * Introduction *
11752 @c ****************
11755 @section Introduction
11758 This chapter describes GNAT's @emph{Project Manager}, a facility that allows
11759 you to manage complex builds involving a number of source files, directories,
11760 and compilation options for different system configurations. In particular,
11761 project files allow you to specify:
11764 The directory or set of directories containing the source files, and/or the
11765 names of the specific source files themselves
11767 The directory in which the compiler's output
11768 (@file{ALI} files, object files, tree files) is to be placed
11770 The directory in which the executable programs is to be placed
11772 ^Switch^Switch^ settings for any of the project-enabled tools
11773 (@command{gnatmake}, compiler, binder, linker, @code{gnatls}, @code{gnatxref},
11774 @code{gnatfind}); you can apply these settings either globally or to individual
11777 The source files containing the main subprogram(s) to be built
11779 The source programming language(s) (currently Ada and/or C)
11781 Source file naming conventions; you can specify these either globally or for
11782 individual compilation units
11789 @node Project Files
11790 @subsection Project Files
11793 Project files are written in a syntax close to that of Ada, using familiar
11794 notions such as packages, context clauses, declarations, default values,
11795 assignments, and inheritance. Finally, project files can be built
11796 hierarchically from other project files, simplifying complex system
11797 integration and project reuse.
11799 A @dfn{project} is a specific set of values for various compilation properties.
11800 The settings for a given project are described by means of
11801 a @dfn{project file}, which is a text file written in an Ada-like syntax.
11802 Property values in project files are either strings or lists of strings.
11803 Properties that are not explicitly set receive default values. A project
11804 file may interrogate the values of @dfn{external variables} (user-defined
11805 command-line switches or environment variables), and it may specify property
11806 settings conditionally, based on the value of such variables.
11808 In simple cases, a project's source files depend only on other source files
11809 in the same project, or on the predefined libraries. (@emph{Dependence} is
11811 the Ada technical sense; as in one Ada unit @code{with}ing another.) However,
11812 the Project Manager also allows more sophisticated arrangements,
11813 where the source files in one project depend on source files in other
11817 One project can @emph{import} other projects containing needed source files.
11819 You can organize GNAT projects in a hierarchy: a @emph{child} project
11820 can extend a @emph{parent} project, inheriting the parent's source files and
11821 optionally overriding any of them with alternative versions
11825 More generally, the Project Manager lets you structure large development
11826 efforts into hierarchical subsystems, where build decisions are delegated
11827 to the subsystem level, and thus different compilation environments
11828 (^switch^switch^ settings) used for different subsystems.
11830 The Project Manager is invoked through the
11831 @option{^-P^/PROJECT_FILE=^@emph{projectfile}}
11832 switch to @command{gnatmake} or to the @command{^gnat^GNAT^} front driver.
11834 There may be zero, one or more spaces between @option{-P} and
11835 @option{@emph{projectfile}}.
11837 If you want to define (on the command line) an external variable that is
11838 queried by the project file, you must use the
11839 @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
11840 The Project Manager parses and interprets the project file, and drives the
11841 invoked tool based on the project settings.
11843 The Project Manager supports a wide range of development strategies,
11844 for systems of all sizes. Here are some typical practices that are
11848 Using a common set of source files, but generating object files in different
11849 directories via different ^switch^switch^ settings
11851 Using a mostly-shared set of source files, but with different versions of
11856 The destination of an executable can be controlled inside a project file
11857 using the @option{^-o^-o^}
11859 In the absence of such a ^switch^switch^ either inside
11860 the project file or on the command line, any executable files generated by
11861 @command{gnatmake} are placed in the directory @code{Exec_Dir} specified
11862 in the project file. If no @code{Exec_Dir} is specified, they will be placed
11863 in the object directory of the project.
11865 You can use project files to achieve some of the effects of a source
11866 versioning system (for example, defining separate projects for
11867 the different sets of sources that comprise different releases) but the
11868 Project Manager is independent of any source configuration management tools
11869 that might be used by the developers.
11871 The next section introduces the main features of GNAT's project facility
11872 through a sequence of examples; subsequent sections will present the syntax
11873 and semantics in more detail. A more formal description of the project
11874 facility appears in @ref{Project File Reference,,, gnat_rm, GNAT
11877 @c *****************************
11878 @c * Examples of Project Files *
11879 @c *****************************
11881 @node Examples of Project Files
11882 @section Examples of Project Files
11884 This section illustrates some of the typical uses of project files and
11885 explains their basic structure and behavior.
11888 * Common Sources with Different ^Switches^Switches^ and Directories::
11889 * Using External Variables::
11890 * Importing Other Projects::
11891 * Extending a Project::
11894 @node Common Sources with Different ^Switches^Switches^ and Directories
11895 @subsection Common Sources with Different ^Switches^Switches^ and Directories
11899 * Specifying the Object Directory::
11900 * Specifying the Exec Directory::
11901 * Project File Packages::
11902 * Specifying ^Switch^Switch^ Settings::
11903 * Main Subprograms::
11904 * Executable File Names::
11905 * Source File Naming Conventions::
11906 * Source Language(s)::
11910 Suppose that the Ada source files @file{pack.ads}, @file{pack.adb}, and
11911 @file{proc.adb} are in the @file{/common} directory. The file
11912 @file{proc.adb} contains an Ada main subprogram @code{Proc} that @code{with}s
11913 package @code{Pack}. We want to compile these source files under two sets
11914 of ^switches^switches^:
11917 When debugging, we want to pass the @option{-g} switch to @command{gnatmake},
11918 and the @option{^-gnata^-gnata^},
11919 @option{^-gnato^-gnato^},
11920 and @option{^-gnatE^-gnatE^} switches to the
11921 compiler; the compiler's output is to appear in @file{/common/debug}
11923 When preparing a release version, we want to pass the @option{^-O2^O2^} switch
11924 to the compiler; the compiler's output is to appear in @file{/common/release}
11928 The GNAT project files shown below, respectively @file{debug.gpr} and
11929 @file{release.gpr} in the @file{/common} directory, achieve these effects.
11942 ^/common/debug^[COMMON.DEBUG]^
11947 ^/common/release^[COMMON.RELEASE]^
11952 Here are the corresponding project files:
11954 @smallexample @c projectfile
11957 for Object_Dir use "debug";
11958 for Main use ("proc");
11961 for ^Default_Switches^Default_Switches^ ("Ada")
11963 for Executable ("proc.adb") use "proc1";
11968 package Compiler is
11969 for ^Default_Switches^Default_Switches^ ("Ada")
11970 use ("-fstack-check",
11973 "^-gnatE^-gnatE^");
11979 @smallexample @c projectfile
11982 for Object_Dir use "release";
11983 for Exec_Dir use ".";
11984 for Main use ("proc");
11986 package Compiler is
11987 for ^Default_Switches^Default_Switches^ ("Ada")
11995 The name of the project defined by @file{debug.gpr} is @code{"Debug"} (case
11996 insensitive), and analogously the project defined by @file{release.gpr} is
11997 @code{"Release"}. For consistency the file should have the same name as the
11998 project, and the project file's extension should be @code{"gpr"}. These
11999 conventions are not required, but a warning is issued if they are not followed.
12001 If the current directory is @file{^/temp^[TEMP]^}, then the command
12003 gnatmake ^-P/common/debug.gpr^/PROJECT_FILE=[COMMON]DEBUG^
12007 generates object and ALI files in @file{^/common/debug^[COMMON.DEBUG]^},
12008 as well as the @code{^proc1^PROC1.EXE^} executable,
12009 using the ^switch^switch^ settings defined in the project file.
12011 Likewise, the command
12013 gnatmake ^-P/common/release.gpr^/PROJECT_FILE=[COMMON]RELEASE^
12017 generates object and ALI files in @file{^/common/release^[COMMON.RELEASE]^},
12018 and the @code{^proc^PROC.EXE^}
12019 executable in @file{^/common^[COMMON]^},
12020 using the ^switch^switch^ settings from the project file.
12023 @unnumberedsubsubsec Source Files
12026 If a project file does not explicitly specify a set of source directories or
12027 a set of source files, then by default the project's source files are the
12028 Ada source files in the project file directory. Thus @file{pack.ads},
12029 @file{pack.adb}, and @file{proc.adb} are the source files for both projects.
12031 @node Specifying the Object Directory
12032 @unnumberedsubsubsec Specifying the Object Directory
12035 Several project properties are modeled by Ada-style @emph{attributes};
12036 a property is defined by supplying the equivalent of an Ada attribute
12037 definition clause in the project file.
12038 A project's object directory is another such a property; the corresponding
12039 attribute is @code{Object_Dir}, and its value is also a string expression,
12040 specified either as absolute or relative. In the later case,
12041 it is relative to the project file directory. Thus the compiler's
12042 output is directed to @file{^/common/debug^[COMMON.DEBUG]^}
12043 (for the @code{Debug} project)
12044 and to @file{^/common/release^[COMMON.RELEASE]^}
12045 (for the @code{Release} project).
12046 If @code{Object_Dir} is not specified, then the default is the project file
12049 @node Specifying the Exec Directory
12050 @unnumberedsubsubsec Specifying the Exec Directory
12053 A project's exec directory is another property; the corresponding
12054 attribute is @code{Exec_Dir}, and its value is also a string expression,
12055 either specified as relative or absolute. If @code{Exec_Dir} is not specified,
12056 then the default is the object directory (which may also be the project file
12057 directory if attribute @code{Object_Dir} is not specified). Thus the executable
12058 is placed in @file{^/common/debug^[COMMON.DEBUG]^}
12059 for the @code{Debug} project (attribute @code{Exec_Dir} not specified)
12060 and in @file{^/common^[COMMON]^} for the @code{Release} project.
12062 @node Project File Packages
12063 @unnumberedsubsubsec Project File Packages
12066 A GNAT tool that is integrated with the Project Manager is modeled by a
12067 corresponding package in the project file. In the example above,
12068 The @code{Debug} project defines the packages @code{Builder}
12069 (for @command{gnatmake}) and @code{Compiler};
12070 the @code{Release} project defines only the @code{Compiler} package.
12072 The Ada-like package syntax is not to be taken literally. Although packages in
12073 project files bear a surface resemblance to packages in Ada source code, the
12074 notation is simply a way to convey a grouping of properties for a named
12075 entity. Indeed, the package names permitted in project files are restricted
12076 to a predefined set, corresponding to the project-aware tools, and the contents
12077 of packages are limited to a small set of constructs.
12078 The packages in the example above contain attribute definitions.
12080 @node Specifying ^Switch^Switch^ Settings
12081 @unnumberedsubsubsec Specifying ^Switch^Switch^ Settings
12084 ^Switch^Switch^ settings for a project-aware tool can be specified through
12085 attributes in the package that corresponds to the tool.
12086 The example above illustrates one of the relevant attributes,
12087 @code{^Default_Switches^Default_Switches^}, which is defined in packages
12088 in both project files.
12089 Unlike simple attributes like @code{Source_Dirs},
12090 @code{^Default_Switches^Default_Switches^} is
12091 known as an @emph{associative array}. When you define this attribute, you must
12092 supply an ``index'' (a literal string), and the effect of the attribute
12093 definition is to set the value of the array at the specified index.
12094 For the @code{^Default_Switches^Default_Switches^} attribute,
12095 the index is a programming language (in our case, Ada),
12096 and the value specified (after @code{use}) must be a list
12097 of string expressions.
12099 The attributes permitted in project files are restricted to a predefined set.
12100 Some may appear at project level, others in packages.
12101 For any attribute that is an associative array, the index must always be a
12102 literal string, but the restrictions on this string (e.g., a file name or a
12103 language name) depend on the individual attribute.
12104 Also depending on the attribute, its specified value will need to be either a
12105 string or a string list.
12107 In the @code{Debug} project, we set the switches for two tools,
12108 @command{gnatmake} and the compiler, and thus we include the two corresponding
12109 packages; each package defines the @code{^Default_Switches^Default_Switches^}
12110 attribute with index @code{"Ada"}.
12111 Note that the package corresponding to
12112 @command{gnatmake} is named @code{Builder}. The @code{Release} project is
12113 similar, but only includes the @code{Compiler} package.
12115 In project @code{Debug} above, the ^switches^switches^ starting with
12116 @option{-gnat} that are specified in package @code{Compiler}
12117 could have been placed in package @code{Builder}, since @command{gnatmake}
12118 transmits all such ^switches^switches^ to the compiler.
12120 @node Main Subprograms
12121 @unnumberedsubsubsec Main Subprograms
12124 One of the specifiable properties of a project is a list of files that contain
12125 main subprograms. This property is captured in the @code{Main} attribute,
12126 whose value is a list of strings. If a project defines the @code{Main}
12127 attribute, it is not necessary to identify the main subprogram(s) when
12128 invoking @command{gnatmake} (@pxref{gnatmake and Project Files}).
12130 @node Executable File Names
12131 @unnumberedsubsubsec Executable File Names
12134 By default, the executable file name corresponding to a main source is
12135 deduced from the main source file name. Through the attributes
12136 @code{Executable} and @code{Executable_Suffix} of package @code{Builder},
12137 it is possible to change this default.
12138 In project @code{Debug} above, the executable file name
12139 for main source @file{^proc.adb^PROC.ADB^} is
12140 @file{^proc1^PROC1.EXE^}.
12141 Attribute @code{Executable_Suffix}, when specified, may change the suffix
12142 of the executable files, when no attribute @code{Executable} applies:
12143 its value replace the platform-specific executable suffix.
12144 Attributes @code{Executable} and @code{Executable_Suffix} are the only ways to
12145 specify a non-default executable file name when several mains are built at once
12146 in a single @command{gnatmake} command.
12148 @node Source File Naming Conventions
12149 @unnumberedsubsubsec Source File Naming Conventions
12152 Since the project files above do not specify any source file naming
12153 conventions, the GNAT defaults are used. The mechanism for defining source
12154 file naming conventions -- a package named @code{Naming} --
12155 is described below (@pxref{Naming Schemes}).
12157 @node Source Language(s)
12158 @unnumberedsubsubsec Source Language(s)
12161 Since the project files do not specify a @code{Languages} attribute, by
12162 default the GNAT tools assume that the language of the project file is Ada.
12163 More generally, a project can comprise source files
12164 in Ada, C, and/or other languages.
12166 @node Using External Variables
12167 @subsection Using External Variables
12170 Instead of supplying different project files for debug and release, we can
12171 define a single project file that queries an external variable (set either
12172 on the command line or via an ^environment variable^logical name^) in order to
12173 conditionally define the appropriate settings. Again, assume that the
12174 source files @file{pack.ads}, @file{pack.adb}, and @file{proc.adb} are
12175 located in directory @file{^/common^[COMMON]^}. The following project file,
12176 @file{build.gpr}, queries the external variable named @code{STYLE} and
12177 defines an object directory and ^switch^switch^ settings based on whether
12178 the value is @code{"deb"} (debug) or @code{"rel"} (release), and where
12179 the default is @code{"deb"}.
12181 @smallexample @c projectfile
12184 for Main use ("proc");
12186 type Style_Type is ("deb", "rel");
12187 Style : Style_Type := external ("STYLE", "deb");
12191 for Object_Dir use "debug";
12194 for Object_Dir use "release";
12195 for Exec_Dir use ".";
12204 for ^Default_Switches^Default_Switches^ ("Ada")
12206 for Executable ("proc") use "proc1";
12215 package Compiler is
12219 for ^Default_Switches^Default_Switches^ ("Ada")
12220 use ("^-gnata^-gnata^",
12222 "^-gnatE^-gnatE^");
12225 for ^Default_Switches^Default_Switches^ ("Ada")
12236 @code{Style_Type} is an example of a @emph{string type}, which is the project
12237 file analog of an Ada enumeration type but whose components are string literals
12238 rather than identifiers. @code{Style} is declared as a variable of this type.
12240 The form @code{external("STYLE", "deb")} is known as an
12241 @emph{external reference}; its first argument is the name of an
12242 @emph{external variable}, and the second argument is a default value to be
12243 used if the external variable doesn't exist. You can define an external
12244 variable on the command line via the @option{^-X^/EXTERNAL_REFERENCE^} switch,
12245 or you can use ^an environment variable^a logical name^
12246 as an external variable.
12248 Each @code{case} construct is expanded by the Project Manager based on the
12249 value of @code{Style}. Thus the command
12252 gnatmake -P/common/build.gpr -XSTYLE=deb
12258 gnatmake /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=deb
12263 is equivalent to the @command{gnatmake} invocation using the project file
12264 @file{debug.gpr} in the earlier example. So is the command
12266 gnatmake ^-P/common/build.gpr^/PROJECT_FILE=[COMMON]BUILD.GPR^
12270 since @code{"deb"} is the default for @code{STYLE}.
12276 gnatmake -P/common/build.gpr -XSTYLE=rel
12282 GNAT MAKE /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=rel
12287 is equivalent to the @command{gnatmake} invocation using the project file
12288 @file{release.gpr} in the earlier example.
12290 @node Importing Other Projects
12291 @subsection Importing Other Projects
12292 @cindex @code{ADA_PROJECT_PATH}
12293 @cindex @code{GPR_PROJECT_PATH}
12296 A compilation unit in a source file in one project may depend on compilation
12297 units in source files in other projects. To compile this unit under
12298 control of a project file, the
12299 dependent project must @emph{import} the projects containing the needed source
12301 This effect is obtained using syntax similar to an Ada @code{with} clause,
12302 but where @code{with}ed entities are strings that denote project files.
12304 As an example, suppose that the two projects @code{GUI_Proj} and
12305 @code{Comm_Proj} are defined in the project files @file{gui_proj.gpr} and
12306 @file{comm_proj.gpr} in directories @file{^/gui^[GUI]^}
12307 and @file{^/comm^[COMM]^}, respectively.
12308 Suppose that the source files for @code{GUI_Proj} are
12309 @file{gui.ads} and @file{gui.adb}, and that the source files for
12310 @code{Comm_Proj} are @file{comm.ads} and @file{comm.adb}, where each set of
12311 files is located in its respective project file directory. Schematically:
12330 We want to develop an application in directory @file{^/app^[APP]^} that
12331 @code{with} the packages @code{GUI} and @code{Comm}, using the properties of
12332 the corresponding project files (e.g.@: the ^switch^switch^ settings
12333 and object directory).
12334 Skeletal code for a main procedure might be something like the following:
12336 @smallexample @c ada
12339 procedure App_Main is
12348 Here is a project file, @file{app_proj.gpr}, that achieves the desired
12351 @smallexample @c projectfile
12353 with "/gui/gui_proj", "/comm/comm_proj";
12354 project App_Proj is
12355 for Main use ("app_main");
12361 Building an executable is achieved through the command:
12363 gnatmake ^-P/app/app_proj^/PROJECT_FILE=[APP]APP_PROJ^
12366 which will generate the @code{^app_main^APP_MAIN.EXE^} executable
12367 in the directory where @file{app_proj.gpr} resides.
12369 If an imported project file uses the standard extension (@code{^gpr^GPR^}) then
12370 (as illustrated above) the @code{with} clause can omit the extension.
12372 Our example specified an absolute path for each imported project file.
12373 Alternatively, the directory name of an imported object can be omitted
12377 The imported project file is in the same directory as the importing project
12380 You have defined one or two ^environment variables^logical names^
12381 that includes the directory containing
12382 the needed project file. The syntax of @code{GPR_PROJECT_PATH} and
12383 @code{ADA_PROJECT_PATH} is the same as
12384 the syntax of @code{ADA_INCLUDE_PATH} and @code{ADA_OBJECTS_PATH}: a list of
12385 directory names separated by colons (semicolons on Windows).
12389 Thus, if we define @code{ADA_PROJECT_PATH} or @code{GPR_PROJECT_PATH}
12390 to include @file{^/gui^[GUI]^} and
12391 @file{^/comm^[COMM]^}, then our project file @file{app_proj.gpr} can be written
12394 @smallexample @c projectfile
12396 with "gui_proj", "comm_proj";
12397 project App_Proj is
12398 for Main use ("app_main");
12404 Importing other projects can create ambiguities.
12405 For example, the same unit might be present in different imported projects, or
12406 it might be present in both the importing project and in an imported project.
12407 Both of these conditions are errors. Note that in the current version of
12408 the Project Manager, it is illegal to have an ambiguous unit even if the
12409 unit is never referenced by the importing project. This restriction may be
12410 relaxed in a future release.
12412 @node Extending a Project
12413 @subsection Extending a Project
12416 In large software systems it is common to have multiple
12417 implementations of a common interface; in Ada terms, multiple versions of a
12418 package body for the same spec. For example, one implementation
12419 might be safe for use in tasking programs, while another might only be used
12420 in sequential applications. This can be modeled in GNAT using the concept
12421 of @emph{project extension}. If one project (the ``child'') @emph{extends}
12422 another project (the ``parent'') then by default all source files of the
12423 parent project are inherited by the child, but the child project can
12424 override any of the parent's source files with new versions, and can also
12425 add new files. This facility is the project analog of a type extension in
12426 Object-Oriented Programming. Project hierarchies are permitted (a child
12427 project may be the parent of yet another project), and a project that
12428 inherits one project can also import other projects.
12430 As an example, suppose that directory @file{^/seq^[SEQ]^} contains the project
12431 file @file{seq_proj.gpr} as well as the source files @file{pack.ads},
12432 @file{pack.adb}, and @file{proc.adb}:
12445 Note that the project file can simply be empty (that is, no attribute or
12446 package is defined):
12448 @smallexample @c projectfile
12450 project Seq_Proj is
12456 implying that its source files are all the Ada source files in the project
12459 Suppose we want to supply an alternate version of @file{pack.adb}, in
12460 directory @file{^/tasking^[TASKING]^}, but use the existing versions of
12461 @file{pack.ads} and @file{proc.adb}. We can define a project
12462 @code{Tasking_Proj} that inherits @code{Seq_Proj}:
12466 ^/tasking^[TASKING]^
12472 project Tasking_Proj extends "/seq/seq_proj" is
12478 The version of @file{pack.adb} used in a build depends on which project file
12481 Note that we could have obtained the desired behavior using project import
12482 rather than project inheritance; a @code{base} project would contain the
12483 sources for @file{pack.ads} and @file{proc.adb}, a sequential project would
12484 import @code{base} and add @file{pack.adb}, and likewise a tasking project
12485 would import @code{base} and add a different version of @file{pack.adb}. The
12486 choice depends on whether other sources in the original project need to be
12487 overridden. If they do, then project extension is necessary, otherwise,
12488 importing is sufficient.
12491 In a project file that extends another project file, it is possible to
12492 indicate that an inherited source is not part of the sources of the extending
12493 project. This is necessary sometimes when a package spec has been overloaded
12494 and no longer requires a body: in this case, it is necessary to indicate that
12495 the inherited body is not part of the sources of the project, otherwise there
12496 will be a compilation error when compiling the spec.
12498 For that purpose, the attribute @code{Excluded_Source_Files} is used.
12499 Its value is a string list: a list of file names. It is also possible to use
12500 attribute @code{Excluded_Source_List_File}. Its value is a single string:
12501 the file name of a text file containing a list of file names, one per line.
12503 @smallexample @c @projectfile
12504 project B extends "a" is
12505 for Source_Files use ("pkg.ads");
12506 -- New spec of Pkg does not need a completion
12507 for Excluded_Source_Files use ("pkg.adb");
12511 Attribute @code{Excluded_Source_Files} may also be used to check if a source
12512 is still needed: if it is possible to build using @command{gnatmake} when such
12513 a source is put in attribute @code{Excluded_Source_Files} of a project P, then
12514 it is possible to remove the source completely from a system that includes
12517 @c ***********************
12518 @c * Project File Syntax *
12519 @c ***********************
12521 @node Project File Syntax
12522 @section Project File Syntax
12526 * Qualified Projects::
12532 * Associative Array Attributes::
12533 * case Constructions::
12537 This section describes the structure of project files.
12539 A project may be an @emph{independent project}, entirely defined by a single
12540 project file. Any Ada source file in an independent project depends only
12541 on the predefined library and other Ada source files in the same project.
12544 A project may also @dfn{depend on} other projects, in either or both of
12545 the following ways:
12547 @item It may import any number of projects
12548 @item It may extend at most one other project
12552 The dependence relation is a directed acyclic graph (the subgraph reflecting
12553 the ``extends'' relation is a tree).
12555 A project's @dfn{immediate sources} are the source files directly defined by
12556 that project, either implicitly by residing in the project file's directory,
12557 or explicitly through any of the source-related attributes described below.
12558 More generally, a project @var{proj}'s @dfn{sources} are the immediate sources
12559 of @var{proj} together with the immediate sources (unless overridden) of any
12560 project on which @var{proj} depends (either directly or indirectly).
12563 @subsection Basic Syntax
12566 As seen in the earlier examples, project files have an Ada-like syntax.
12567 The minimal project file is:
12568 @smallexample @c projectfile
12577 The identifier @code{Empty} is the name of the project.
12578 This project name must be present after the reserved
12579 word @code{end} at the end of the project file, followed by a semi-colon.
12581 Any name in a project file, such as the project name or a variable name,
12582 has the same syntax as an Ada identifier.
12584 The reserved words of project files are the Ada 95 reserved words plus
12585 @code{extends}, @code{external}, and @code{project}. Note that the only Ada
12586 reserved words currently used in project file syntax are:
12622 Comments in project files have the same syntax as in Ada, two consecutive
12623 hyphens through the end of the line.
12625 @node Qualified Projects
12626 @subsection Qualified Projects
12629 Before the reserved @code{project}, there may be one or two "qualifiers", that
12630 is identifiers or other reserved words, to qualify the project.
12632 The current list of qualifiers is:
12636 @code{abstract}: qualify a project with no sources. A qualified abstract
12637 project must either have no declaration of attributes @code{Source_Dirs},
12638 @code{Source_Files}, @code{Languages} or @code{Source_List_File}, or one of
12639 @code{Source_Dirs}, @code{Source_Files}, or @code{Languages} must be declared
12640 as empty. If it extends another project, the project it extends must also be a
12641 qualified abstract project.
12644 @code{standard}: a standard project is a non library project with sources.
12647 @code{aggregate}: for future extension
12650 @code{aggregate library}: for future extension
12653 @code{library}: a library project must declare both attributes
12654 @code{Library_Name} and @code{Library_Dir}.
12657 @code{configuration}: a configuration project cannot be in a project tree.
12661 @subsection Packages
12664 A project file may contain @emph{packages}. The name of a package must be one
12665 of the identifiers from the following list. A package
12666 with a given name may only appear once in a project file. Package names are
12667 case insensitive. The following package names are legal:
12683 @code{Cross_Reference}
12687 @code{Pretty_Printer}
12697 @code{Language_Processing}
12701 In its simplest form, a package may be empty:
12703 @smallexample @c projectfile
12713 A package may contain @emph{attribute declarations},
12714 @emph{variable declarations} and @emph{case constructions}, as will be
12717 When there is ambiguity between a project name and a package name,
12718 the name always designates the project. To avoid possible confusion, it is
12719 always a good idea to avoid naming a project with one of the
12720 names allowed for packages or any name that starts with @code{gnat}.
12723 @subsection Expressions
12726 An @emph{expression} is either a @emph{string expression} or a
12727 @emph{string list expression}.
12729 A @emph{string expression} is either a @emph{simple string expression} or a
12730 @emph{compound string expression}.
12732 A @emph{simple string expression} is one of the following:
12734 @item A literal string; e.g.@: @code{"comm/my_proj.gpr"}
12735 @item A string-valued variable reference (@pxref{Variables})
12736 @item A string-valued attribute reference (@pxref{Attributes})
12737 @item An external reference (@pxref{External References in Project Files})
12741 A @emph{compound string expression} is a concatenation of string expressions,
12742 using the operator @code{"&"}
12744 Path & "/" & File_Name & ".ads"
12748 A @emph{string list expression} is either a
12749 @emph{simple string list expression} or a
12750 @emph{compound string list expression}.
12752 A @emph{simple string list expression} is one of the following:
12754 @item A parenthesized list of zero or more string expressions,
12755 separated by commas
12757 File_Names := (File_Name, "gnat.adc", File_Name & ".orig");
12760 @item A string list-valued variable reference
12761 @item A string list-valued attribute reference
12765 A @emph{compound string list expression} is the concatenation (using
12766 @code{"&"}) of a simple string list expression and an expression. Note that
12767 each term in a compound string list expression, except the first, may be
12768 either a string expression or a string list expression.
12770 @smallexample @c projectfile
12772 File_Name_List := () & File_Name; -- One string in this list
12773 Extended_File_Name_List := File_Name_List & (File_Name & ".orig");
12775 Big_List := File_Name_List & Extended_File_Name_List;
12776 -- Concatenation of two string lists: three strings
12777 Illegal_List := "gnat.adc" & Extended_File_Name_List;
12778 -- Illegal: must start with a string list
12783 @subsection String Types
12786 A @emph{string type declaration} introduces a discrete set of string literals.
12787 If a string variable is declared to have this type, its value
12788 is restricted to the given set of literals.
12790 Here is an example of a string type declaration:
12792 @smallexample @c projectfile
12793 type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS");
12797 Variables of a string type are called @emph{typed variables}; all other
12798 variables are called @emph{untyped variables}. Typed variables are
12799 particularly useful in @code{case} constructions, to support conditional
12800 attribute declarations.
12801 (@pxref{case Constructions}).
12803 The string literals in the list are case sensitive and must all be different.
12804 They may include any graphic characters allowed in Ada, including spaces.
12806 A string type may only be declared at the project level, not inside a package.
12808 A string type may be referenced by its name if it has been declared in the same
12809 project file, or by an expanded name whose prefix is the name of the project
12810 in which it is declared.
12813 @subsection Variables
12816 A variable may be declared at the project file level, or within a package.
12817 Here are some examples of variable declarations:
12819 @smallexample @c projectfile
12821 This_OS : OS := external ("OS"); -- a typed variable declaration
12822 That_OS := "GNU/Linux"; -- an untyped variable declaration
12827 The syntax of a @emph{typed variable declaration} is identical to the Ada
12828 syntax for an object declaration. By contrast, the syntax of an untyped
12829 variable declaration is identical to an Ada assignment statement. In fact,
12830 variable declarations in project files have some of the characteristics of
12831 an assignment, in that successive declarations for the same variable are
12832 allowed. Untyped variable declarations do establish the expected kind of the
12833 variable (string or string list), and successive declarations for it must
12834 respect the initial kind.
12837 A string variable declaration (typed or untyped) declares a variable
12838 whose value is a string. This variable may be used as a string expression.
12839 @smallexample @c projectfile
12840 File_Name := "readme.txt";
12841 Saved_File_Name := File_Name & ".saved";
12845 A string list variable declaration declares a variable whose value is a list
12846 of strings. The list may contain any number (zero or more) of strings.
12848 @smallexample @c projectfile
12850 List_With_One_Element := ("^-gnaty^-gnaty^");
12851 List_With_Two_Elements := List_With_One_Element & "^-gnatg^-gnatg^";
12852 Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"
12853 "pack2.ada", "util_.ada", "util.ada");
12857 The same typed variable may not be declared more than once at project level,
12858 and it may not be declared more than once in any package; it is in effect
12861 The same untyped variable may be declared several times. Declarations are
12862 elaborated in the order in which they appear, so the new value replaces
12863 the old one, and any subsequent reference to the variable uses the new value.
12864 However, as noted above, if a variable has been declared as a string, all
12866 declarations must give it a string value. Similarly, if a variable has
12867 been declared as a string list, all subsequent declarations
12868 must give it a string list value.
12870 A @emph{variable reference} may take several forms:
12873 @item The simple variable name, for a variable in the current package (if any)
12874 or in the current project
12875 @item An expanded name, whose prefix is a context name.
12879 A @emph{context} may be one of the following:
12882 @item The name of an existing package in the current project
12883 @item The name of an imported project of the current project
12884 @item The name of an ancestor project (i.e., a project extended by the current
12885 project, either directly or indirectly)
12886 @item An expanded name whose prefix is an imported/parent project name, and
12887 whose selector is a package name in that project.
12891 A variable reference may be used in an expression.
12894 @subsection Attributes
12897 A project (and its packages) may have @emph{attributes} that define
12898 the project's properties. Some attributes have values that are strings;
12899 others have values that are string lists.
12901 There are two categories of attributes: @emph{simple attributes}
12902 and @emph{associative arrays} (@pxref{Associative Array Attributes}).
12904 Legal project attribute names, and attribute names for each legal package are
12905 listed below. Attributes names are case-insensitive.
12907 The following attributes are defined on projects (all are simple attributes):
12909 @multitable @columnfractions .4 .3
12910 @item @emph{Attribute Name}
12912 @item @code{Source_Files}
12914 @item @code{Source_Dirs}
12916 @item @code{Source_List_File}
12918 @item @code{Object_Dir}
12920 @item @code{Exec_Dir}
12922 @item @code{Excluded_Source_Dirs}
12924 @item @code{Excluded_Source_Files}
12926 @item @code{Excluded_Source_List_File}
12928 @item @code{Languages}
12932 @item @code{Library_Dir}
12934 @item @code{Library_Name}
12936 @item @code{Library_Kind}
12938 @item @code{Library_Version}
12940 @item @code{Library_Interface}
12942 @item @code{Library_Auto_Init}
12944 @item @code{Library_Options}
12946 @item @code{Library_Src_Dir}
12948 @item @code{Library_ALI_Dir}
12950 @item @code{Library_GCC}
12952 @item @code{Library_Symbol_File}
12954 @item @code{Library_Symbol_Policy}
12956 @item @code{Library_Reference_Symbol_File}
12958 @item @code{Externally_Built}
12963 The following attributes are defined for package @code{Naming}
12964 (@pxref{Naming Schemes}):
12966 @multitable @columnfractions .4 .2 .2 .2
12967 @item Attribute Name @tab Category @tab Index @tab Value
12968 @item @code{Spec_Suffix}
12969 @tab associative array
12972 @item @code{Body_Suffix}
12973 @tab associative array
12976 @item @code{Separate_Suffix}
12977 @tab simple attribute
12980 @item @code{Casing}
12981 @tab simple attribute
12984 @item @code{Dot_Replacement}
12985 @tab simple attribute
12989 @tab associative array
12993 @tab associative array
12996 @item @code{Specification_Exceptions}
12997 @tab associative array
13000 @item @code{Implementation_Exceptions}
13001 @tab associative array
13007 The following attributes are defined for packages @code{Builder},
13008 @code{Compiler}, @code{Binder},
13009 @code{Linker}, @code{Cross_Reference}, and @code{Finder}
13010 (@pxref{^Switches^Switches^ and Project Files}).
13012 @multitable @columnfractions .4 .2 .2 .2
13013 @item Attribute Name @tab Category @tab Index @tab Value
13014 @item @code{^Default_Switches^Default_Switches^}
13015 @tab associative array
13018 @item @code{^Switches^Switches^}
13019 @tab associative array
13025 In addition, package @code{Compiler} has a single string attribute
13026 @code{Local_Configuration_Pragmas} and package @code{Builder} has a single
13027 string attribute @code{Global_Configuration_Pragmas}.
13030 Each simple attribute has a default value: the empty string (for string-valued
13031 attributes) and the empty list (for string list-valued attributes).
13033 An attribute declaration defines a new value for an attribute.
13035 Examples of simple attribute declarations:
13037 @smallexample @c projectfile
13038 for Object_Dir use "objects";
13039 for Source_Dirs use ("units", "test/drivers");
13043 The syntax of a @dfn{simple attribute declaration} is similar to that of an
13044 attribute definition clause in Ada.
13046 Attributes references may be appear in expressions.
13047 The general form for such a reference is @code{<entity>'<attribute>}:
13048 Associative array attributes are functions. Associative
13049 array attribute references must have an argument that is a string literal.
13053 @smallexample @c projectfile
13055 Naming'Dot_Replacement
13056 Imported_Project'Source_Dirs
13057 Imported_Project.Naming'Casing
13058 Builder'^Default_Switches^Default_Switches^("Ada")
13062 The prefix of an attribute may be:
13064 @item @code{project} for an attribute of the current project
13065 @item The name of an existing package of the current project
13066 @item The name of an imported project
13067 @item The name of a parent project that is extended by the current project
13068 @item An expanded name whose prefix is imported/parent project name,
13069 and whose selector is a package name
13074 @smallexample @c projectfile
13077 for Source_Dirs use project'Source_Dirs & "units";
13078 for Source_Dirs use project'Source_Dirs & "test/drivers"
13084 In the first attribute declaration, initially the attribute @code{Source_Dirs}
13085 has the default value: an empty string list. After this declaration,
13086 @code{Source_Dirs} is a string list of one element: @code{"units"}.
13087 After the second attribute declaration @code{Source_Dirs} is a string list of
13088 two elements: @code{"units"} and @code{"test/drivers"}.
13090 Note: this example is for illustration only. In practice,
13091 the project file would contain only one attribute declaration:
13093 @smallexample @c projectfile
13094 for Source_Dirs use ("units", "test/drivers");
13097 @node Associative Array Attributes
13098 @subsection Associative Array Attributes
13101 Some attributes are defined as @emph{associative arrays}. An associative
13102 array may be regarded as a function that takes a string as a parameter
13103 and delivers a string or string list value as its result.
13105 Here are some examples of single associative array attribute associations:
13107 @smallexample @c projectfile
13108 for Body ("main") use "Main.ada";
13109 for ^Switches^Switches^ ("main.ada")
13111 "^-gnatv^-gnatv^");
13112 for ^Switches^Switches^ ("main.ada")
13113 use Builder'^Switches^Switches^ ("main.ada")
13118 Like untyped variables and simple attributes, associative array attributes
13119 may be declared several times. Each declaration supplies a new value for the
13120 attribute, and replaces the previous setting.
13123 An associative array attribute may be declared as a full associative array
13124 declaration, with the value of the same attribute in an imported or extended
13127 @smallexample @c projectfile
13129 for Default_Switches use Default.Builder'Default_Switches;
13134 In this example, @code{Default} must be either a project imported by the
13135 current project, or the project that the current project extends. If the
13136 attribute is in a package (in this case, in package @code{Builder}), the same
13137 package needs to be specified.
13140 A full associative array declaration replaces any other declaration for the
13141 attribute, including other full associative array declaration. Single
13142 associative array associations may be declare after a full associative
13143 declaration, modifying the value for a single association of the attribute.
13145 @node case Constructions
13146 @subsection @code{case} Constructions
13149 A @code{case} construction is used in a project file to effect conditional
13151 Here is a typical example:
13153 @smallexample @c projectfile
13156 type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS");
13158 OS : OS_Type := external ("OS", "GNU/Linux");
13162 package Compiler is
13164 when "GNU/Linux" | "Unix" =>
13165 for ^Default_Switches^Default_Switches^ ("Ada")
13166 use ("^-gnath^-gnath^");
13168 for ^Default_Switches^Default_Switches^ ("Ada")
13169 use ("^-gnatP^-gnatP^");
13178 The syntax of a @code{case} construction is based on the Ada case statement
13179 (although there is no @code{null} construction for empty alternatives).
13181 The case expression must be a typed string variable.
13182 Each alternative comprises the reserved word @code{when}, either a list of
13183 literal strings separated by the @code{"|"} character or the reserved word
13184 @code{others}, and the @code{"=>"} token.
13185 Each literal string must belong to the string type that is the type of the
13187 An @code{others} alternative, if present, must occur last.
13189 After each @code{=>}, there are zero or more constructions. The only
13190 constructions allowed in a case construction are other case constructions,
13191 attribute declarations and variable declarations. String type declarations and
13192 package declarations are not allowed. Variable declarations are restricted to
13193 variables that have already been declared before the case construction.
13195 The value of the case variable is often given by an external reference
13196 (@pxref{External References in Project Files}).
13198 @c ****************************************
13199 @c * Objects and Sources in Project Files *
13200 @c ****************************************
13202 @node Objects and Sources in Project Files
13203 @section Objects and Sources in Project Files
13206 * Object Directory::
13208 * Source Directories::
13209 * Source File Names::
13213 Each project has exactly one object directory and one or more source
13214 directories. The source directories must contain at least one source file,
13215 unless the project file explicitly specifies that no source files are present
13216 (@pxref{Source File Names}).
13218 @node Object Directory
13219 @subsection Object Directory
13222 The object directory for a project is the directory containing the compiler's
13223 output (such as @file{ALI} files and object files) for the project's immediate
13226 The object directory is given by the value of the attribute @code{Object_Dir}
13227 in the project file.
13229 @smallexample @c projectfile
13230 for Object_Dir use "objects";
13234 The attribute @code{Object_Dir} has a string value, the path name of the object
13235 directory. The path name may be absolute or relative to the directory of the
13236 project file. This directory must already exist, and be readable and writable.
13238 By default, when the attribute @code{Object_Dir} is not given an explicit value
13239 or when its value is the empty string, the object directory is the same as the
13240 directory containing the project file.
13242 @node Exec Directory
13243 @subsection Exec Directory
13246 The exec directory for a project is the directory containing the executables
13247 for the project's main subprograms.
13249 The exec directory is given by the value of the attribute @code{Exec_Dir}
13250 in the project file.
13252 @smallexample @c projectfile
13253 for Exec_Dir use "executables";
13257 The attribute @code{Exec_Dir} has a string value, the path name of the exec
13258 directory. The path name may be absolute or relative to the directory of the
13259 project file. This directory must already exist, and be writable.
13261 By default, when the attribute @code{Exec_Dir} is not given an explicit value
13262 or when its value is the empty string, the exec directory is the same as the
13263 object directory of the project file.
13265 @node Source Directories
13266 @subsection Source Directories
13269 The source directories of a project are specified by the project file
13270 attribute @code{Source_Dirs}.
13272 This attribute's value is a string list. If the attribute is not given an
13273 explicit value, then there is only one source directory, the one where the
13274 project file resides.
13276 A @code{Source_Dirs} attribute that is explicitly defined to be the empty list,
13279 @smallexample @c projectfile
13280 for Source_Dirs use ();
13284 indicates that the project contains no source files.
13286 Otherwise, each string in the string list designates one or more
13287 source directories.
13289 @smallexample @c projectfile
13290 for Source_Dirs use ("sources", "test/drivers");
13294 If a string in the list ends with @code{"/**"}, then the directory whose path
13295 name precedes the two asterisks, as well as all its subdirectories
13296 (recursively), are source directories.
13298 @smallexample @c projectfile
13299 for Source_Dirs use ("/system/sources/**");
13303 Here the directory @code{/system/sources} and all of its subdirectories
13304 (recursively) are source directories.
13306 To specify that the source directories are the directory of the project file
13307 and all of its subdirectories, you can declare @code{Source_Dirs} as follows:
13308 @smallexample @c projectfile
13309 for Source_Dirs use ("./**");
13313 Each of the source directories must exist and be readable.
13315 @node Source File Names
13316 @subsection Source File Names
13319 In a project that contains source files, their names may be specified by the
13320 attributes @code{Source_Files} (a string list) or @code{Source_List_File}
13321 (a string). Source file names never include any directory information.
13323 If the attribute @code{Source_Files} is given an explicit value, then each
13324 element of the list is a source file name.
13326 @smallexample @c projectfile
13327 for Source_Files use ("main.adb");
13328 for Source_Files use ("main.adb", "pack1.ads", "pack2.adb");
13332 If the attribute @code{Source_Files} is not given an explicit value,
13333 but the attribute @code{Source_List_File} is given a string value,
13334 then the source file names are contained in the text file whose path name
13335 (absolute or relative to the directory of the project file) is the
13336 value of the attribute @code{Source_List_File}.
13338 Each line in the file that is not empty or is not a comment
13339 contains a source file name.
13341 @smallexample @c projectfile
13342 for Source_List_File use "source_list.txt";
13346 By default, if neither the attribute @code{Source_Files} nor the attribute
13347 @code{Source_List_File} is given an explicit value, then each file in the
13348 source directories that conforms to the project's naming scheme
13349 (@pxref{Naming Schemes}) is an immediate source of the project.
13351 A warning is issued if both attributes @code{Source_Files} and
13352 @code{Source_List_File} are given explicit values. In this case, the attribute
13353 @code{Source_Files} prevails.
13355 Each source file name must be the name of one existing source file
13356 in one of the source directories.
13358 A @code{Source_Files} attribute whose value is an empty list
13359 indicates that there are no source files in the project.
13361 If the order of the source directories is known statically, that is if
13362 @code{"/**"} is not used in the string list @code{Source_Dirs}, then there may
13363 be several files with the same source file name. In this case, only the file
13364 in the first directory is considered as an immediate source of the project
13365 file. If the order of the source directories is not known statically, it is
13366 an error to have several files with the same source file name.
13368 Projects can be specified to have no Ada source
13369 files: the value of @code{Source_Dirs} or @code{Source_Files} may be an empty
13370 list, or the @code{"Ada"} may be absent from @code{Languages}:
13372 @smallexample @c projectfile
13373 for Source_Dirs use ();
13374 for Source_Files use ();
13375 for Languages use ("C", "C++");
13379 Otherwise, a project must contain at least one immediate source.
13381 Projects with no source files are useful as template packages
13382 (@pxref{Packages in Project Files}) for other projects; in particular to
13383 define a package @code{Naming} (@pxref{Naming Schemes}).
13385 @c ****************************
13386 @c * Importing Projects *
13387 @c ****************************
13389 @node Importing Projects
13390 @section Importing Projects
13391 @cindex @code{ADA_PROJECT_PATH}
13392 @cindex @code{GPR_PROJECT_PATH}
13395 An immediate source of a project P may depend on source files that
13396 are neither immediate sources of P nor in the predefined library.
13397 To get this effect, P must @emph{import} the projects that contain the needed
13400 @smallexample @c projectfile
13402 with "project1", "utilities.gpr";
13403 with "/namings/apex.gpr";
13410 As can be seen in this example, the syntax for importing projects is similar
13411 to the syntax for importing compilation units in Ada. However, project files
13412 use literal strings instead of names, and the @code{with} clause identifies
13413 project files rather than packages.
13415 Each literal string is the file name or path name (absolute or relative) of a
13416 project file. If a string corresponds to a file name, with no path or a
13417 relative path, then its location is determined by the @emph{project path}. The
13418 latter can be queried using @code{gnatls -v}. It contains:
13422 In first position, the directory containing the current project file.
13424 In last position, the default project directory. This default project directory
13425 is part of the GNAT installation and is the standard place to install project
13426 files giving access to standard support libraries.
13428 @ref{Installing a library}
13432 In between, all the directories referenced in the
13433 ^environment variables^logical names^ @env{GPR_PROJECT_PATH}
13434 and @env{ADA_PROJECT_PATH} if they exist, and in that order.
13438 If a relative pathname is used, as in
13440 @smallexample @c projectfile
13445 then the full path for the project is constructed by concatenating this
13446 relative path to those in the project path, in order, until a matching file is
13447 found. Any symbolic link will be fully resolved in the directory of the
13448 importing project file before the imported project file is examined.
13450 If the @code{with}'ed project file name does not have an extension,
13451 the default is @file{^.gpr^.GPR^}. If a file with this extension is not found,
13452 then the file name as specified in the @code{with} clause (no extension) will
13453 be used. In the above example, if a file @code{project1.gpr} is found, then it
13454 will be used; otherwise, if a file @code{^project1^PROJECT1^} exists
13455 then it will be used; if neither file exists, this is an error.
13457 A warning is issued if the name of the project file does not match the
13458 name of the project; this check is case insensitive.
13460 Any source file that is an immediate source of the imported project can be
13461 used by the immediate sources of the importing project, transitively. Thus
13462 if @code{A} imports @code{B}, and @code{B} imports @code{C}, the immediate
13463 sources of @code{A} may depend on the immediate sources of @code{C}, even if
13464 @code{A} does not import @code{C} explicitly. However, this is not recommended,
13465 because if and when @code{B} ceases to import @code{C}, some sources in
13466 @code{A} will no longer compile.
13468 A side effect of this capability is that normally cyclic dependencies are not
13469 permitted: if @code{A} imports @code{B} (directly or indirectly) then @code{B}
13470 is not allowed to import @code{A}. However, there are cases when cyclic
13471 dependencies would be beneficial. For these cases, another form of import
13472 between projects exists, the @code{limited with}: a project @code{A} that
13473 imports a project @code{B} with a straight @code{with} may also be imported,
13474 directly or indirectly, by @code{B} on the condition that imports from @code{B}
13475 to @code{A} include at least one @code{limited with}.
13477 @smallexample @c 0projectfile
13483 limited with "../a/a.gpr";
13491 limited with "../a/a.gpr";
13497 In the above legal example, there are two project cycles:
13500 @item A -> C -> D -> A
13504 In each of these cycle there is one @code{limited with}: import of @code{A}
13505 from @code{B} and import of @code{A} from @code{D}.
13507 The difference between straight @code{with} and @code{limited with} is that
13508 the name of a project imported with a @code{limited with} cannot be used in the
13509 project that imports it. In particular, its packages cannot be renamed and
13510 its variables cannot be referred to.
13512 An exception to the above rules for @code{limited with} is that for the main
13513 project specified to @command{gnatmake} or to the @command{GNAT} driver a
13514 @code{limited with} is equivalent to a straight @code{with}. For example,
13515 in the example above, projects @code{B} and @code{D} could not be main
13516 projects for @command{gnatmake} or to the @command{GNAT} driver, because they
13517 each have a @code{limited with} that is the only one in a cycle of importing
13520 @c *********************
13521 @c * Project Extension *
13522 @c *********************
13524 @node Project Extension
13525 @section Project Extension
13528 During development of a large system, it is sometimes necessary to use
13529 modified versions of some of the source files, without changing the original
13530 sources. This can be achieved through the @emph{project extension} facility.
13532 @smallexample @c projectfile
13533 project Modified_Utilities extends "/baseline/utilities.gpr" is @dots{}
13537 A project extension declaration introduces an extending project
13538 (the @emph{child}) and a project being extended (the @emph{parent}).
13540 By default, a child project inherits all the sources of its parent.
13541 However, inherited sources can be overridden: a unit in a parent is hidden
13542 by a unit of the same name in the child.
13544 Inherited sources are considered to be sources (but not immediate sources)
13545 of the child project; see @ref{Project File Syntax}.
13547 An inherited source file retains any switches specified in the parent project.
13549 For example if the project @code{Utilities} contains the spec and the
13550 body of an Ada package @code{Util_IO}, then the project
13551 @code{Modified_Utilities} can contain a new body for package @code{Util_IO}.
13552 The original body of @code{Util_IO} will not be considered in program builds.
13553 However, the package spec will still be found in the project
13556 A child project can have only one parent, except when it is qualified as
13557 abstract. But it may import any number of other projects.
13559 A project is not allowed to import directly or indirectly at the same time a
13560 child project and any of its ancestors.
13562 @c *******************************
13563 @c * Project Hierarchy Extension *
13564 @c *******************************
13566 @node Project Hierarchy Extension
13567 @section Project Hierarchy Extension
13570 When extending a large system spanning multiple projects, it is often
13571 inconvenient to extend every project in the hierarchy that is impacted by a
13572 small change introduced. In such cases, it is possible to create a virtual
13573 extension of entire hierarchy using @code{extends all} relationship.
13575 When the project is extended using @code{extends all} inheritance, all projects
13576 that are imported by it, both directly and indirectly, are considered virtually
13577 extended. That is, the Project Manager creates "virtual projects"
13578 that extend every project in the hierarchy; all these virtual projects have
13579 no sources of their own and have as object directory the object directory of
13580 the root of "extending all" project.
13582 It is possible to explicitly extend one or more projects in the hierarchy
13583 in order to modify the sources. These extending projects must be imported by
13584 the "extending all" project, which will replace the corresponding virtual
13585 projects with the explicit ones.
13587 When building such a project hierarchy extension, the Project Manager will
13588 ensure that both modified sources and sources in virtual extending projects
13589 that depend on them, are recompiled.
13591 By means of example, consider the following hierarchy of projects.
13595 project A, containing package P1
13597 project B importing A and containing package P2 which depends on P1
13599 project C importing B and containing package P3 which depends on P2
13603 We want to modify packages P1 and P3.
13605 This project hierarchy will need to be extended as follows:
13609 Create project A1 that extends A, placing modified P1 there:
13611 @smallexample @c 0projectfile
13612 project A1 extends "(@dots{})/A" is
13617 Create project C1 that "extends all" C and imports A1, placing modified
13620 @smallexample @c 0projectfile
13621 with "(@dots{})/A1";
13622 project C1 extends all "(@dots{})/C" is
13627 When you build project C1, your entire modified project space will be
13628 recompiled, including the virtual project B1 that has been impacted by the
13629 "extending all" inheritance of project C.
13631 Note that if a Library Project in the hierarchy is virtually extended,
13632 the virtual project that extends the Library Project is not a Library Project.
13634 @c ****************************************
13635 @c * External References in Project Files *
13636 @c ****************************************
13638 @node External References in Project Files
13639 @section External References in Project Files
13642 A project file may contain references to external variables; such references
13643 are called @emph{external references}.
13645 An external variable is either defined as part of the environment (an
13646 environment variable in Unix, for example) or else specified on the command
13647 line via the @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
13648 If both, then the command line value is used.
13650 The value of an external reference is obtained by means of the built-in
13651 function @code{external}, which returns a string value.
13652 This function has two forms:
13654 @item @code{external (external_variable_name)}
13655 @item @code{external (external_variable_name, default_value)}
13659 Each parameter must be a string literal. For example:
13661 @smallexample @c projectfile
13663 external ("OS", "GNU/Linux")
13667 In the form with one parameter, the function returns the value of
13668 the external variable given as parameter. If this name is not present in the
13669 environment, the function returns an empty string.
13671 In the form with two string parameters, the second argument is
13672 the value returned when the variable given as the first argument is not
13673 present in the environment. In the example above, if @code{"OS"} is not
13674 the name of ^an environment variable^a logical name^ and is not passed on
13675 the command line, then the returned value is @code{"GNU/Linux"}.
13677 An external reference may be part of a string expression or of a string
13678 list expression, and can therefore appear in a variable declaration or
13679 an attribute declaration.
13681 @smallexample @c projectfile
13683 type Mode_Type is ("Debug", "Release");
13684 Mode : Mode_Type := external ("MODE");
13691 @c *****************************
13692 @c * Packages in Project Files *
13693 @c *****************************
13695 @node Packages in Project Files
13696 @section Packages in Project Files
13699 A @emph{package} defines the settings for project-aware tools within a
13701 For each such tool one can declare a package; the names for these
13702 packages are preset (@pxref{Packages}).
13703 A package may contain variable declarations, attribute declarations, and case
13706 @smallexample @c projectfile
13709 package Builder is -- used by gnatmake
13710 for ^Default_Switches^Default_Switches^ ("Ada")
13719 The syntax of package declarations mimics that of package in Ada.
13721 Most of the packages have an attribute
13722 @code{^Default_Switches^Default_Switches^}.
13723 This attribute is an associative array, and its value is a string list.
13724 The index of the associative array is the name of a programming language (case
13725 insensitive). This attribute indicates the ^switch^switch^
13726 or ^switches^switches^ to be used
13727 with the corresponding tool.
13729 Some packages also have another attribute, @code{^Switches^Switches^},
13730 an associative array whose value is a string list.
13731 The index is the name of a source file.
13732 This attribute indicates the ^switch^switch^
13733 or ^switches^switches^ to be used by the corresponding
13734 tool when dealing with this specific file.
13736 Further information on these ^switch^switch^-related attributes is found in
13737 @ref{^Switches^Switches^ and Project Files}.
13739 A package may be declared as a @emph{renaming} of another package; e.g., from
13740 the project file for an imported project.
13742 @smallexample @c projectfile
13744 with "/global/apex.gpr";
13746 package Naming renames Apex.Naming;
13753 Packages that are renamed in other project files often come from project files
13754 that have no sources: they are just used as templates. Any modification in the
13755 template will be reflected automatically in all the project files that rename
13756 a package from the template.
13758 In addition to the tool-oriented packages, you can also declare a package
13759 named @code{Naming} to establish specialized source file naming conventions
13760 (@pxref{Naming Schemes}).
13762 @c ************************************
13763 @c * Variables from Imported Projects *
13764 @c ************************************
13766 @node Variables from Imported Projects
13767 @section Variables from Imported Projects
13770 An attribute or variable defined in an imported or parent project can
13771 be used in expressions in the importing / extending project.
13772 Such an attribute or variable is denoted by an expanded name whose prefix
13773 is either the name of the project or the expanded name of a package within
13776 @smallexample @c projectfile
13779 project Main extends "base" is
13780 Var1 := Imported.Var;
13781 Var2 := Base.Var & ".new";
13786 for ^Default_Switches^Default_Switches^ ("Ada")
13787 use Imported.Builder'Ada_^Switches^Switches^ &
13788 "^-gnatg^-gnatg^" &
13794 package Compiler is
13795 for ^Default_Switches^Default_Switches^ ("Ada")
13796 use Base.Compiler'Ada_^Switches^Switches^;
13807 The value of @code{Var1} is a copy of the variable @code{Var} defined
13808 in the project file @file{"imported.gpr"}
13810 the value of @code{Var2} is a copy of the value of variable @code{Var}
13811 defined in the project file @file{base.gpr}, concatenated with @code{".new"}
13813 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13814 @code{Builder} is a string list that includes in its value a copy of the value
13815 of @code{Ada_^Switches^Switches^} defined in the @code{Builder} package
13816 in project file @file{imported.gpr} plus two new elements:
13817 @option{"^-gnatg^-gnatg^"}
13818 and @option{"^-v^-v^"};
13820 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13821 @code{Compiler} is a copy of the variable @code{Ada_^Switches^Switches^}
13822 defined in the @code{Compiler} package in project file @file{base.gpr},
13823 the project being extended.
13826 @c ******************
13827 @c * Naming Schemes *
13828 @c ******************
13830 @node Naming Schemes
13831 @section Naming Schemes
13834 Sometimes an Ada software system is ported from a foreign compilation
13835 environment to GNAT, and the file names do not use the default GNAT
13836 conventions. Instead of changing all the file names (which for a variety
13837 of reasons might not be possible), you can define the relevant file
13838 naming scheme in the @code{Naming} package in your project file.
13841 Note that the use of pragmas described in
13842 @ref{Alternative File Naming Schemes} by mean of a configuration
13843 pragmas file is not supported when using project files. You must use
13844 the features described in this paragraph. You can however use specify
13845 other configuration pragmas (@pxref{Specifying Configuration Pragmas}).
13848 For example, the following
13849 package models the Apex file naming rules:
13851 @smallexample @c projectfile
13854 for Casing use "lowercase";
13855 for Dot_Replacement use ".";
13856 for Spec_Suffix ("Ada") use ".1.ada";
13857 for Body_Suffix ("Ada") use ".2.ada";
13864 For example, the following package models the HP Ada file naming rules:
13866 @smallexample @c projectfile
13869 for Casing use "lowercase";
13870 for Dot_Replacement use "__";
13871 for Spec_Suffix ("Ada") use "_.^ada^ada^";
13872 for Body_Suffix ("Ada") use ".^ada^ada^";
13878 (Note that @code{Casing} is @code{"lowercase"} because GNAT gets the file
13879 names in lower case)
13883 You can define the following attributes in package @code{Naming}:
13887 @item @code{Casing}
13888 This must be a string with one of the three values @code{"lowercase"},
13889 @code{"uppercase"} or @code{"mixedcase"}; these strings are case insensitive.
13892 If @code{Casing} is not specified, then the default is @code{"lowercase"}.
13894 @item @code{Dot_Replacement}
13895 This must be a string whose value satisfies the following conditions:
13898 @item It must not be empty
13899 @item It cannot start or end with an alphanumeric character
13900 @item It cannot be a single underscore
13901 @item It cannot start with an underscore followed by an alphanumeric
13902 @item It cannot contain a dot @code{'.'} except if the entire string
13907 If @code{Dot_Replacement} is not specified, then the default is @code{"-"}.
13909 @item @code{Spec_Suffix}
13910 This is an associative array (indexed by the programming language name, case
13911 insensitive) whose value is a string that must satisfy the following
13915 @item It must not be empty
13916 @item It must include at least one dot
13919 If @code{Spec_Suffix ("Ada")} is not specified, then the default is
13920 @code{"^.ads^.ADS^"}.
13922 @item @code{Body_Suffix}
13923 This is an associative array (indexed by the programming language name, case
13924 insensitive) whose value is a string that must satisfy the following
13928 @item It must not be empty
13929 @item It must include at least one dot
13930 @item It cannot be the same as @code{Spec_Suffix ("Ada")}
13933 If @code{Body_Suffix ("Ada")} and @code{Spec_Suffix ("Ada")} end with the
13934 same string, then a file name that ends with the longest of these two suffixes
13935 will be a body if the longest suffix is @code{Body_Suffix ("Ada")} or a spec
13936 if the longest suffix is @code{Spec_Suffix ("Ada")}.
13938 If the suffix does not start with a '.', a file with a name exactly equal
13939 to the suffix will also be part of the project (for instance if you define
13940 the suffix as @code{Makefile}, a file called @file{Makefile} will be part
13941 of the project. This is not interesting in general when using projects to
13942 compile. However, it might become useful when a project is also used to
13943 find the list of source files in an editor, like the GNAT Programming System
13946 If @code{Body_Suffix ("Ada")} is not specified, then the default is
13947 @code{"^.adb^.ADB^"}.
13949 @item @code{Separate_Suffix}
13950 This must be a string whose value satisfies the same conditions as
13951 @code{Body_Suffix}. The same "longest suffix" rules apply.
13954 If @code{Separate_Suffix ("Ada")} is not specified, then it defaults to same
13955 value as @code{Body_Suffix ("Ada")}.
13959 You can use the associative array attribute @code{Spec} to define
13960 the source file name for an individual Ada compilation unit's spec. The array
13961 index must be a string literal that identifies the Ada unit (case insensitive).
13962 The value of this attribute must be a string that identifies the file that
13963 contains this unit's spec (case sensitive or insensitive depending on the
13966 @smallexample @c projectfile
13967 for Spec ("MyPack.MyChild") use "mypack.mychild.spec";
13970 When the source file contains several units, you can indicate at what
13971 position the unit occurs in the file, with the following. The first unit
13972 in the file has index 1
13974 @smallexample @c projectfile
13975 for Body ("top") use "foo.a" at 1;
13976 for Body ("foo") use "foo.a" at 2;
13981 You can use the associative array attribute @code{Body} to
13982 define the source file name for an individual Ada compilation unit's body
13983 (possibly a subunit). The array index must be a string literal that identifies
13984 the Ada unit (case insensitive). The value of this attribute must be a string
13985 that identifies the file that contains this unit's body or subunit (case
13986 sensitive or insensitive depending on the operating system).
13988 @smallexample @c projectfile
13989 for Body ("MyPack.MyChild") use "mypack.mychild.body";
13993 @c ********************
13994 @c * Library Projects *
13995 @c ********************
13997 @node Library Projects
13998 @section Library Projects
14001 @emph{Library projects} are projects whose object code is placed in a library.
14002 (Note that this facility is not yet supported on all platforms).
14004 @code{gnatmake} or @code{gprbuild} will collect all object files into a
14005 single archive, which might either be a shared or a static library. This
14006 library can later on be linked with multiple executables, potentially
14007 reducing their sizes.
14009 If your project file specifies languages other than Ada, but you are still
14010 using @code{gnatmake} to compile and link, the latter will not try to
14011 compile your sources other than Ada (you should use @code{gprbuild} if that
14012 is your intent). However, @code{gnatmake} will automatically link all object
14013 files found in the object directory, whether or not they were compiled from
14014 an Ada source file. This specific behavior only applies when multiple
14015 languages are specified.
14017 To create a library project, you need to define in its project file
14018 two project-level attributes: @code{Library_Name} and @code{Library_Dir}.
14019 Additionally, you may define other library-related attributes such as
14020 @code{Library_Kind}, @code{Library_Version}, @code{Library_Interface},
14021 @code{Library_Auto_Init}, @code{Library_Options} and @code{Library_GCC}.
14023 The @code{Library_Name} attribute has a string value. There is no restriction
14024 on the name of a library. It is the responsibility of the developer to
14025 choose a name that will be accepted by the platform. It is recommended to
14026 choose names that could be Ada identifiers; such names are almost guaranteed
14027 to be acceptable on all platforms.
14029 The @code{Library_Dir} attribute has a string value that designates the path
14030 (absolute or relative) of the directory where the library will reside.
14031 It must designate an existing directory, and this directory must be writable,
14032 different from the project's object directory and from any source directory
14033 in the project tree.
14035 If both @code{Library_Name} and @code{Library_Dir} are specified and
14036 are legal, then the project file defines a library project. The optional
14037 library-related attributes are checked only for such project files.
14039 The @code{Library_Kind} attribute has a string value that must be one of the
14040 following (case insensitive): @code{"static"}, @code{"dynamic"} or
14041 @code{"relocatable"} (which is a synonym for @code{"dynamic"}). If this
14042 attribute is not specified, the library is a static library, that is
14043 an archive of object files that can be potentially linked into a
14044 static executable. Otherwise, the library may be dynamic or
14045 relocatable, that is a library that is loaded only at the start of execution.
14047 If you need to build both a static and a dynamic library, you should use two
14048 different object directories, since in some cases some extra code needs to
14049 be generated for the latter. For such cases, it is recommended to either use
14050 two different project files, or a single one which uses external variables
14051 to indicate what kind of library should be build.
14053 The @code{Library_ALI_Dir} attribute may be specified to indicate the
14054 directory where the ALI files of the library will be copied. When it is
14055 not specified, the ALI files are copied to the directory specified in
14056 attribute @code{Library_Dir}. The directory specified by @code{Library_ALI_Dir}
14057 must be writable and different from the project's object directory and from
14058 any source directory in the project tree.
14060 The @code{Library_Version} attribute has a string value whose interpretation
14061 is platform dependent. It has no effect on VMS and Windows. On Unix, it is
14062 used only for dynamic/relocatable libraries as the internal name of the
14063 library (the @code{"soname"}). If the library file name (built from the
14064 @code{Library_Name}) is different from the @code{Library_Version}, then the
14065 library file will be a symbolic link to the actual file whose name will be
14066 @code{Library_Version}.
14070 @smallexample @c projectfile
14076 for Library_Dir use "lib_dir";
14077 for Library_Name use "dummy";
14078 for Library_Kind use "relocatable";
14079 for Library_Version use "libdummy.so." & Version;
14086 Directory @file{lib_dir} will contain the internal library file whose name
14087 will be @file{libdummy.so.1}, and @file{libdummy.so} will be a symbolic link to
14088 @file{libdummy.so.1}.
14090 When @command{gnatmake} detects that a project file
14091 is a library project file, it will check all immediate sources of the project
14092 and rebuild the library if any of the sources have been recompiled.
14094 Standard project files can import library project files. In such cases,
14095 the libraries will only be rebuilt if some of its sources are recompiled
14096 because they are in the closure of some other source in an importing project.
14097 Sources of the library project files that are not in such a closure will
14098 not be checked, unless the full library is checked, because one of its sources
14099 needs to be recompiled.
14101 For instance, assume the project file @code{A} imports the library project file
14102 @code{L}. The immediate sources of A are @file{a1.adb}, @file{a2.ads} and
14103 @file{a2.adb}. The immediate sources of L are @file{l1.ads}, @file{l1.adb},
14104 @file{l2.ads}, @file{l2.adb}.
14106 If @file{l1.adb} has been modified, then the library associated with @code{L}
14107 will be rebuilt when compiling all the immediate sources of @code{A} only
14108 if @file{a1.ads}, @file{a2.ads} or @file{a2.adb} includes a statement
14111 To be sure that all the sources in the library associated with @code{L} are
14112 up to date, and that all the sources of project @code{A} are also up to date,
14113 the following two commands needs to be used:
14120 When a library is built or rebuilt, an attempt is made first to delete all
14121 files in the library directory.
14122 All @file{ALI} files will also be copied from the object directory to the
14123 library directory. To build executables, @command{gnatmake} will use the
14124 library rather than the individual object files.
14127 It is also possible to create library project files for third-party libraries
14128 that are precompiled and cannot be compiled locally thanks to the
14129 @code{externally_built} attribute. (See @ref{Installing a library}).
14132 @c *******************************
14133 @c * Stand-alone Library Projects *
14134 @c *******************************
14136 @node Stand-alone Library Projects
14137 @section Stand-alone Library Projects
14140 A Stand-alone Library is a library that contains the necessary code to
14141 elaborate the Ada units that are included in the library. A Stand-alone
14142 Library is suitable to be used in an executable when the main is not
14143 in Ada. However, Stand-alone Libraries may also be used with an Ada main
14146 A Stand-alone Library Project is a Library Project where the library is
14147 a Stand-alone Library.
14149 To be a Stand-alone Library Project, in addition to the two attributes
14150 that make a project a Library Project (@code{Library_Name} and
14151 @code{Library_Dir}, see @ref{Library Projects}), the attribute
14152 @code{Library_Interface} must be defined.
14154 @smallexample @c projectfile
14156 for Library_Dir use "lib_dir";
14157 for Library_Name use "dummy";
14158 for Library_Interface use ("int1", "int1.child");
14162 Attribute @code{Library_Interface} has a nonempty string list value,
14163 each string in the list designating a unit contained in an immediate source
14164 of the project file.
14166 When a Stand-alone Library is built, first the binder is invoked to build
14167 a package whose name depends on the library name
14168 (^b~dummy.ads/b^B$DUMMY.ADS/B^ in the example above).
14169 This binder-generated package includes initialization and
14170 finalization procedures whose
14171 names depend on the library name (dummyinit and dummyfinal in the example
14172 above). The object corresponding to this package is included in the library.
14174 A dynamic or relocatable Stand-alone Library is automatically initialized
14175 if automatic initialization of Stand-alone Libraries is supported on the
14176 platform and if attribute @code{Library_Auto_Init} is not specified or
14177 is specified with the value "true". A static Stand-alone Library is never
14178 automatically initialized.
14180 Single string attribute @code{Library_Auto_Init} may be specified with only
14181 two possible values: "false" or "true" (case-insensitive). Specifying
14182 "false" for attribute @code{Library_Auto_Init} will prevent automatic
14183 initialization of dynamic or relocatable libraries.
14185 When a non-automatically initialized Stand-alone Library is used
14186 in an executable, its initialization procedure must be called before
14187 any service of the library is used.
14188 When the main subprogram is in Ada, it may mean that the initialization
14189 procedure has to be called during elaboration of another package.
14191 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
14192 (those that are listed in attribute @code{Library_Interface}) are copied to
14193 the Library Directory. As a consequence, only the Interface Units may be
14194 imported from Ada units outside of the library. If other units are imported,
14195 the binding phase will fail.
14197 When a Stand-Alone Library is bound, the switches that are specified in
14198 the attribute @code{Default_Switches ("Ada")} in package @code{Binder} are
14199 used in the call to @command{gnatbind}.
14201 The string list attribute @code{Library_Options} may be used to specified
14202 additional switches to the call to @command{gcc} to link the library.
14204 The attribute @code{Library_Src_Dir}, may be specified for a
14205 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
14206 single string value. Its value must be the path (absolute or relative to the
14207 project directory) of an existing directory. This directory cannot be the
14208 object directory or one of the source directories, but it can be the same as
14209 the library directory. The sources of the Interface
14210 Units of the library, necessary to an Ada client of the library, will be
14211 copied to the designated directory, called Interface Copy directory.
14212 These sources includes the specs of the Interface Units, but they may also
14213 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
14214 are used, or when there is a generic units in the spec. Before the sources
14215 are copied to the Interface Copy directory, an attempt is made to delete all
14216 files in the Interface Copy directory.
14218 @c *************************************
14219 @c * Switches Related to Project Files *
14220 @c *************************************
14221 @node Switches Related to Project Files
14222 @section Switches Related to Project Files
14225 The following switches are used by GNAT tools that support project files:
14229 @item ^-P^/PROJECT_FILE=^@var{project}
14230 @cindex @option{^-P^/PROJECT_FILE^} (any project-aware tool)
14231 Indicates the name of a project file. This project file will be parsed with
14232 the verbosity indicated by @option{^-vP^MESSAGE_PROJECT_FILES=^@emph{x}},
14233 if any, and using the external references indicated
14234 by @option{^-X^/EXTERNAL_REFERENCE^} switches, if any.
14236 There may zero, one or more spaces between @option{-P} and @var{project}.
14240 There must be only one @option{^-P^/PROJECT_FILE^} switch on the command line.
14243 Since the Project Manager parses the project file only after all the switches
14244 on the command line are checked, the order of the switches
14245 @option{^-P^/PROJECT_FILE^},
14246 @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}}
14247 or @option{^-X^/EXTERNAL_REFERENCE^} is not significant.
14249 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
14250 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (any project-aware tool)
14251 Indicates that external variable @var{name} has the value @var{value}.
14252 The Project Manager will use this value for occurrences of
14253 @code{external(name)} when parsing the project file.
14257 If @var{name} or @var{value} includes a space, then @var{name=value} should be
14258 put between quotes.
14266 Several @option{^-X^/EXTERNAL_REFERENCE^} switches can be used simultaneously.
14267 If several @option{^-X^/EXTERNAL_REFERENCE^} switches specify the same
14268 @var{name}, only the last one is used.
14271 An external variable specified with a @option{^-X^/EXTERNAL_REFERENCE^} switch
14272 takes precedence over the value of the same name in the environment.
14274 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
14275 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (any project-aware tool)
14276 Indicates the verbosity of the parsing of GNAT project files.
14279 @option{-vP0} means Default;
14280 @option{-vP1} means Medium;
14281 @option{-vP2} means High.
14285 There are three possible options for this qualifier: DEFAULT, MEDIUM and
14290 The default is ^Default^DEFAULT^: no output for syntactically correct
14293 If several @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}} switches are present,
14294 only the last one is used.
14296 @item ^-aP^/ADD_PROJECT_SEARCH_DIR=^<dir>
14297 @cindex @option{^-aP^/ADD_PROJECT_SEARCH_DIR=^} (any project-aware tool)
14298 Add directory <dir> at the beginning of the project search path, in order,
14299 after the current working directory.
14303 @cindex @option{-eL} (any project-aware tool)
14304 Follow all symbolic links when processing project files.
14307 @item ^--subdirs^/SUBDIRS^=<subdir>
14308 @cindex @option{^--subdirs^/SUBDIRS^=} (gnatmake and gnatclean)
14309 This switch is recognized by gnatmake and gnatclean. It indicate that the real
14310 directories (except the source directories) are the subdirectories <subdir>
14311 of the directories specified in the project files. This applies in particular
14312 to object directories, library directories and exec directories. If the
14313 subdirectories do not exist, they are created automatically.
14317 @c **********************************
14318 @c * Tools Supporting Project Files *
14319 @c **********************************
14321 @node Tools Supporting Project Files
14322 @section Tools Supporting Project Files
14325 * gnatmake and Project Files::
14326 * The GNAT Driver and Project Files::
14329 @node gnatmake and Project Files
14330 @subsection gnatmake and Project Files
14333 This section covers several topics related to @command{gnatmake} and
14334 project files: defining ^switches^switches^ for @command{gnatmake}
14335 and for the tools that it invokes; specifying configuration pragmas;
14336 the use of the @code{Main} attribute; building and rebuilding library project
14340 * ^Switches^Switches^ and Project Files::
14341 * Specifying Configuration Pragmas::
14342 * Project Files and Main Subprograms::
14343 * Library Project Files::
14346 @node ^Switches^Switches^ and Project Files
14347 @subsubsection ^Switches^Switches^ and Project Files
14350 It is not currently possible to specify VMS style qualifiers in the project
14351 files; only Unix style ^switches^switches^ may be specified.
14355 For each of the packages @code{Builder}, @code{Compiler}, @code{Binder}, and
14356 @code{Linker}, you can specify a @code{^Default_Switches^Default_Switches^}
14357 attribute, a @code{^Switches^Switches^} attribute, or both;
14358 as their names imply, these ^switch^switch^-related
14359 attributes affect the ^switches^switches^ that are used for each of these GNAT
14361 @command{gnatmake} is invoked. As will be explained below, these
14362 component-specific ^switches^switches^ precede
14363 the ^switches^switches^ provided on the @command{gnatmake} command line.
14365 The @code{^Default_Switches^Default_Switches^} attribute is an associative
14366 array indexed by language name (case insensitive) whose value is a string list.
14369 @smallexample @c projectfile
14371 package Compiler is
14372 for ^Default_Switches^Default_Switches^ ("Ada")
14373 use ("^-gnaty^-gnaty^",
14380 The @code{^Switches^Switches^} attribute is also an associative array,
14381 indexed by a file name (which may or may not be case sensitive, depending
14382 on the operating system) whose value is a string list. For example:
14384 @smallexample @c projectfile
14387 for ^Switches^Switches^ ("main1.adb")
14389 for ^Switches^Switches^ ("main2.adb")
14396 For the @code{Builder} package, the file names must designate source files
14397 for main subprograms. For the @code{Binder} and @code{Linker} packages, the
14398 file names must designate @file{ALI} or source files for main subprograms.
14399 In each case just the file name without an explicit extension is acceptable.
14401 For each tool used in a program build (@command{gnatmake}, the compiler, the
14402 binder, and the linker), the corresponding package @dfn{contributes} a set of
14403 ^switches^switches^ for each file on which the tool is invoked, based on the
14404 ^switch^switch^-related attributes defined in the package.
14405 In particular, the ^switches^switches^
14406 that each of these packages contributes for a given file @var{f} comprise:
14410 the value of attribute @code{^Switches^Switches^ (@var{f})},
14411 if it is specified in the package for the given file,
14413 otherwise, the value of @code{^Default_Switches^Default_Switches^ ("Ada")},
14414 if it is specified in the package.
14418 If neither of these attributes is defined in the package, then the package does
14419 not contribute any ^switches^switches^ for the given file.
14421 When @command{gnatmake} is invoked on a file, the ^switches^switches^ comprise
14422 two sets, in the following order: those contributed for the file
14423 by the @code{Builder} package;
14424 and the switches passed on the command line.
14426 When @command{gnatmake} invokes a tool (compiler, binder, linker) on a file,
14427 the ^switches^switches^ passed to the tool comprise three sets,
14428 in the following order:
14432 the applicable ^switches^switches^ contributed for the file
14433 by the @code{Builder} package in the project file supplied on the command line;
14436 those contributed for the file by the package (in the relevant project file --
14437 see below) corresponding to the tool; and
14440 the applicable switches passed on the command line.
14444 The term @emph{applicable ^switches^switches^} reflects the fact that
14445 @command{gnatmake} ^switches^switches^ may or may not be passed to individual
14446 tools, depending on the individual ^switch^switch^.
14448 @command{gnatmake} may invoke the compiler on source files from different
14449 projects. The Project Manager will use the appropriate project file to
14450 determine the @code{Compiler} package for each source file being compiled.
14451 Likewise for the @code{Binder} and @code{Linker} packages.
14453 As an example, consider the following package in a project file:
14455 @smallexample @c projectfile
14458 package Compiler is
14459 for ^Default_Switches^Default_Switches^ ("Ada")
14461 for ^Switches^Switches^ ("a.adb")
14463 for ^Switches^Switches^ ("b.adb")
14465 "^-gnaty^-gnaty^");
14472 If @command{gnatmake} is invoked with this project file, and it needs to
14473 compile, say, the files @file{a.adb}, @file{b.adb}, and @file{c.adb}, then
14474 @file{a.adb} will be compiled with the ^switch^switch^
14475 @option{^-O1^-O1^},
14476 @file{b.adb} with ^switches^switches^
14478 and @option{^-gnaty^-gnaty^},
14479 and @file{c.adb} with @option{^-g^-g^}.
14481 The following example illustrates the ordering of the ^switches^switches^
14482 contributed by different packages:
14484 @smallexample @c projectfile
14488 for ^Switches^Switches^ ("main.adb")
14496 package Compiler is
14497 for ^Switches^Switches^ ("main.adb")
14505 If you issue the command:
14508 gnatmake ^-Pproj2^/PROJECT_FILE=PROJ2^ -O0 main
14512 then the compiler will be invoked on @file{main.adb} with the following
14513 sequence of ^switches^switches^
14516 ^-g -O1 -O2 -O0^-g -O1 -O2 -O0^
14519 with the last @option{^-O^-O^}
14520 ^switch^switch^ having precedence over the earlier ones;
14521 several other ^switches^switches^
14522 (such as @option{^-c^-c^}) are added implicitly.
14524 The ^switches^switches^
14526 and @option{^-O1^-O1^} are contributed by package
14527 @code{Builder}, @option{^-O2^-O2^} is contributed
14528 by the package @code{Compiler}
14529 and @option{^-O0^-O0^} comes from the command line.
14531 The @option{^-g^-g^}
14532 ^switch^switch^ will also be passed in the invocation of
14533 @command{Gnatlink.}
14535 A final example illustrates switch contributions from packages in different
14538 @smallexample @c projectfile
14541 for Source_Files use ("pack.ads", "pack.adb");
14542 package Compiler is
14543 for ^Default_Switches^Default_Switches^ ("Ada")
14544 use ("^-gnata^-gnata^");
14552 for Source_Files use ("foo_main.adb", "bar_main.adb");
14554 for ^Switches^Switches^ ("foo_main.adb")
14562 -- Ada source file:
14564 procedure Foo_Main is
14572 gnatmake ^-PProj4^/PROJECT_FILE=PROJ4^ foo_main.adb -cargs -gnato
14576 then the ^switches^switches^ passed to the compiler for @file{foo_main.adb} are
14577 @option{^-g^-g^} (contributed by the package @code{Proj4.Builder}) and
14578 @option{^-gnato^-gnato^} (passed on the command line).
14579 When the imported package @code{Pack} is compiled, the ^switches^switches^ used
14580 are @option{^-g^-g^} from @code{Proj4.Builder},
14581 @option{^-gnata^-gnata^} (contributed from package @code{Proj3.Compiler},
14582 and @option{^-gnato^-gnato^} from the command line.
14585 When using @command{gnatmake} with project files, some ^switches^switches^ or
14586 arguments may be expressed as relative paths. As the working directory where
14587 compilation occurs may change, these relative paths are converted to absolute
14588 paths. For the ^switches^switches^ found in a project file, the relative paths
14589 are relative to the project file directory, for the switches on the command
14590 line, they are relative to the directory where @command{gnatmake} is invoked.
14591 The ^switches^switches^ for which this occurs are:
14597 ^-aI^-aI^, as well as all arguments that are not switches (arguments to
14599 ^-o^-o^, object files specified in package @code{Linker} or after
14600 -largs on the command line). The exception to this rule is the ^switch^switch^
14601 ^--RTS=^--RTS=^ for which a relative path argument is never converted.
14603 @node Specifying Configuration Pragmas
14604 @subsubsection Specifying Configuration Pragmas
14606 When using @command{gnatmake} with project files, if there exists a file
14607 @file{gnat.adc} that contains configuration pragmas, this file will be
14610 Configuration pragmas can be defined by means of the following attributes in
14611 project files: @code{Global_Configuration_Pragmas} in package @code{Builder}
14612 and @code{Local_Configuration_Pragmas} in package @code{Compiler}.
14614 Both these attributes are single string attributes. Their values is the path
14615 name of a file containing configuration pragmas. If a path name is relative,
14616 then it is relative to the project directory of the project file where the
14617 attribute is defined.
14619 When compiling a source, the configuration pragmas used are, in order,
14620 those listed in the file designated by attribute
14621 @code{Global_Configuration_Pragmas} in package @code{Builder} of the main
14622 project file, if it is specified, and those listed in the file designated by
14623 attribute @code{Local_Configuration_Pragmas} in package @code{Compiler} of
14624 the project file of the source, if it exists.
14626 @node Project Files and Main Subprograms
14627 @subsubsection Project Files and Main Subprograms
14630 When using a project file, you can invoke @command{gnatmake}
14631 with one or several main subprograms, by specifying their source files on the
14635 gnatmake ^-P^/PROJECT_FILE=^prj main1 main2 main3
14639 Each of these needs to be a source file of the same project, except
14640 when the switch ^-u^/UNIQUE^ is used.
14643 When ^-u^/UNIQUE^ is not used, all the mains need to be sources of the
14644 same project, one of the project in the tree rooted at the project specified
14645 on the command line. The package @code{Builder} of this common project, the
14646 "main project" is the one that is considered by @command{gnatmake}.
14649 When ^-u^/UNIQUE^ is used, the specified source files may be in projects
14650 imported directly or indirectly by the project specified on the command line.
14651 Note that if such a source file is not part of the project specified on the
14652 command line, the ^switches^switches^ found in package @code{Builder} of the
14653 project specified on the command line, if any, that are transmitted
14654 to the compiler will still be used, not those found in the project file of
14658 When using a project file, you can also invoke @command{gnatmake} without
14659 explicitly specifying any main, and the effect depends on whether you have
14660 defined the @code{Main} attribute. This attribute has a string list value,
14661 where each element in the list is the name of a source file (the file
14662 extension is optional) that contains a unit that can be a main subprogram.
14664 If the @code{Main} attribute is defined in a project file as a non-empty
14665 string list and the switch @option{^-u^/UNIQUE^} is not used on the command
14666 line, then invoking @command{gnatmake} with this project file but without any
14667 main on the command line is equivalent to invoking @command{gnatmake} with all
14668 the file names in the @code{Main} attribute on the command line.
14671 @smallexample @c projectfile
14674 for Main use ("main1", "main2", "main3");
14680 With this project file, @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^"}
14682 @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^ main1 main2 main3"}.
14684 When the project attribute @code{Main} is not specified, or is specified
14685 as an empty string list, or when the switch @option{-u} is used on the command
14686 line, then invoking @command{gnatmake} with no main on the command line will
14687 result in all immediate sources of the project file being checked, and
14688 potentially recompiled. Depending on the presence of the switch @option{-u},
14689 sources from other project files on which the immediate sources of the main
14690 project file depend are also checked and potentially recompiled. In other
14691 words, the @option{-u} switch is applied to all of the immediate sources of the
14694 When no main is specified on the command line and attribute @code{Main} exists
14695 and includes several mains, or when several mains are specified on the
14696 command line, the default ^switches^switches^ in package @code{Builder} will
14697 be used for all mains, even if there are specific ^switches^switches^
14698 specified for one or several mains.
14700 But the ^switches^switches^ from package @code{Binder} or @code{Linker} will be
14701 the specific ^switches^switches^ for each main, if they are specified.
14703 @node Library Project Files
14704 @subsubsection Library Project Files
14707 When @command{gnatmake} is invoked with a main project file that is a library
14708 project file, it is not allowed to specify one or more mains on the command
14712 When a library project file is specified, switches ^-b^/ACTION=BIND^ and
14713 ^-l^/ACTION=LINK^ have special meanings.
14716 @item ^-b^/ACTION=BIND^ is only allowed for stand-alone libraries. It indicates
14717 to @command{gnatmake} that @command{gnatbind} should be invoked for the
14720 @item ^-l^/ACTION=LINK^ may be used for all library projects. It indicates
14721 to @command{gnatmake} that the binder generated file should be compiled
14722 (in the case of a stand-alone library) and that the library should be built.
14726 @node The GNAT Driver and Project Files
14727 @subsection The GNAT Driver and Project Files
14730 A number of GNAT tools, other than @command{^gnatmake^gnatmake^}
14731 can benefit from project files:
14732 @command{^gnatbind^gnatbind^},
14733 @command{^gnatcheck^gnatcheck^}),
14734 @command{^gnatclean^gnatclean^}),
14735 @command{^gnatelim^gnatelim^},
14736 @command{^gnatfind^gnatfind^},
14737 @command{^gnatlink^gnatlink^},
14738 @command{^gnatls^gnatls^},
14739 @command{^gnatmetric^gnatmetric^},
14740 @command{^gnatpp^gnatpp^},
14741 @command{^gnatstub^gnatstub^},
14742 and @command{^gnatxref^gnatxref^}. However, none of these tools can be invoked
14743 directly with a project file switch (@option{^-P^/PROJECT_FILE=^}).
14744 They must be invoked through the @command{gnat} driver.
14746 The @command{gnat} driver is a wrapper that accepts a number of commands and
14747 calls the corresponding tool. It was designed initially for VMS platforms (to
14748 convert VMS qualifiers to Unix-style switches), but it is now available on all
14751 On non-VMS platforms, the @command{gnat} driver accepts the following commands
14752 (case insensitive):
14756 BIND to invoke @command{^gnatbind^gnatbind^}
14758 CHOP to invoke @command{^gnatchop^gnatchop^}
14760 CLEAN to invoke @command{^gnatclean^gnatclean^}
14762 COMP or COMPILE to invoke the compiler
14764 ELIM to invoke @command{^gnatelim^gnatelim^}
14766 FIND to invoke @command{^gnatfind^gnatfind^}
14768 KR or KRUNCH to invoke @command{^gnatkr^gnatkr^}
14770 LINK to invoke @command{^gnatlink^gnatlink^}
14772 LS or LIST to invoke @command{^gnatls^gnatls^}
14774 MAKE to invoke @command{^gnatmake^gnatmake^}
14776 NAME to invoke @command{^gnatname^gnatname^}
14778 PREP or PREPROCESS to invoke @command{^gnatprep^gnatprep^}
14780 PP or PRETTY to invoke @command{^gnatpp^gnatpp^}
14782 METRIC to invoke @command{^gnatmetric^gnatmetric^}
14784 STUB to invoke @command{^gnatstub^gnatstub^}
14786 XREF to invoke @command{^gnatxref^gnatxref^}
14790 (note that the compiler is invoked using the command
14791 @command{^gnatmake -f -u -c^gnatmake -f -u -c^}).
14794 On non-VMS platforms, between @command{gnat} and the command, two
14795 special switches may be used:
14799 @command{-v} to display the invocation of the tool.
14801 @command{-dn} to prevent the @command{gnat} driver from removing
14802 the temporary files it has created. These temporary files are
14803 configuration files and temporary file list files.
14807 The command may be followed by switches and arguments for the invoked
14811 gnat bind -C main.ali
14817 Switches may also be put in text files, one switch per line, and the text
14818 files may be specified with their path name preceded by '@@'.
14821 gnat bind @@args.txt main.ali
14825 In addition, for commands BIND, COMP or COMPILE, FIND, ELIM, LS or LIST, LINK,
14826 METRIC, PP or PRETTY, STUB and XREF, the project file related switches
14827 (@option{^-P^/PROJECT_FILE^},
14828 @option{^-X^/EXTERNAL_REFERENCE^} and
14829 @option{^-vP^/MESSAGES_PROJECT_FILE=^x}) may be used in addition to
14830 the switches of the invoking tool.
14833 When GNAT PP or GNAT PRETTY is used with a project file, but with no source
14834 specified on the command line, it invokes @command{^gnatpp^gnatpp^} with all
14835 the immediate sources of the specified project file.
14838 When GNAT METRIC is used with a project file, but with no source
14839 specified on the command line, it invokes @command{^gnatmetric^gnatmetric^}
14840 with all the immediate sources of the specified project file and with
14841 @option{^-d^/DIRECTORY^} with the parameter pointing to the object directory
14845 In addition, when GNAT PP, GNAT PRETTY or GNAT METRIC is used with
14846 a project file, no source is specified on the command line and
14847 switch ^-U^/ALL_PROJECTS^ is specified on the command line, then
14848 the underlying tool (^gnatpp^gnatpp^ or
14849 ^gnatmetric^gnatmetric^) is invoked for all sources of all projects,
14850 not only for the immediate sources of the main project.
14852 (-U stands for Universal or Union of the project files of the project tree)
14856 For each of the following commands, there is optionally a corresponding
14857 package in the main project.
14861 package @code{Binder} for command BIND (invoking @code{^gnatbind^gnatbind^})
14864 package @code{Check} for command CHECK (invoking
14865 @code{^gnatcheck^gnatcheck^})
14868 package @code{Compiler} for command COMP or COMPILE (invoking the compiler)
14871 package @code{Cross_Reference} for command XREF (invoking
14872 @code{^gnatxref^gnatxref^})
14875 package @code{Eliminate} for command ELIM (invoking
14876 @code{^gnatelim^gnatelim^})
14879 package @code{Finder} for command FIND (invoking @code{^gnatfind^gnatfind^})
14882 package @code{Gnatls} for command LS or LIST (invoking @code{^gnatls^gnatls^})
14885 package @code{Gnatstub} for command STUB
14886 (invoking @code{^gnatstub^gnatstub^})
14889 package @code{Linker} for command LINK (invoking @code{^gnatlink^gnatlink^})
14892 package @code{Metrics} for command METRIC
14893 (invoking @code{^gnatmetric^gnatmetric^})
14896 package @code{Pretty_Printer} for command PP or PRETTY
14897 (invoking @code{^gnatpp^gnatpp^})
14902 Package @code{Gnatls} has a unique attribute @code{^Switches^Switches^},
14903 a simple variable with a string list value. It contains ^switches^switches^
14904 for the invocation of @code{^gnatls^gnatls^}.
14906 @smallexample @c projectfile
14910 for ^Switches^Switches^
14919 All other packages have two attribute @code{^Switches^Switches^} and
14920 @code{^Default_Switches^Default_Switches^}.
14923 @code{^Switches^Switches^} is an associative array attribute, indexed by the
14924 source file name, that has a string list value: the ^switches^switches^ to be
14925 used when the tool corresponding to the package is invoked for the specific
14929 @code{^Default_Switches^Default_Switches^} is an associative array attribute,
14930 indexed by the programming language that has a string list value.
14931 @code{^Default_Switches^Default_Switches^ ("Ada")} contains the
14932 ^switches^switches^ for the invocation of the tool corresponding
14933 to the package, except if a specific @code{^Switches^Switches^} attribute
14934 is specified for the source file.
14936 @smallexample @c projectfile
14940 for Source_Dirs use ("./**");
14943 for ^Switches^Switches^ use
14950 package Compiler is
14951 for ^Default_Switches^Default_Switches^ ("Ada")
14952 use ("^-gnatv^-gnatv^",
14953 "^-gnatwa^-gnatwa^");
14959 for ^Default_Switches^Default_Switches^ ("Ada")
14967 for ^Default_Switches^Default_Switches^ ("Ada")
14969 for ^Switches^Switches^ ("main.adb")
14978 for ^Default_Switches^Default_Switches^ ("Ada")
14985 package Cross_Reference is
14986 for ^Default_Switches^Default_Switches^ ("Ada")
14991 end Cross_Reference;
14997 With the above project file, commands such as
15000 ^gnat comp -Pproj main^GNAT COMP /PROJECT_FILE=PROJ MAIN^
15001 ^gnat ls -Pproj main^GNAT LIST /PROJECT_FILE=PROJ MAIN^
15002 ^gnat xref -Pproj main^GNAT XREF /PROJECT_FILE=PROJ MAIN^
15003 ^gnat bind -Pproj main.ali^GNAT BIND /PROJECT_FILE=PROJ MAIN.ALI^
15004 ^gnat link -Pproj main.ali^GNAT LINK /PROJECT_FILE=PROJ MAIN.ALI^
15008 will set up the environment properly and invoke the tool with the switches
15009 found in the package corresponding to the tool:
15010 @code{^Default_Switches^Default_Switches^ ("Ada")} for all tools,
15011 except @code{^Switches^Switches^ ("main.adb")}
15012 for @code{^gnatlink^gnatlink^}.
15013 It is also possible to invoke some of the tools,
15014 @code{^gnatcheck^gnatcheck^}),
15015 @code{^gnatmetric^gnatmetric^}),
15016 and @code{^gnatpp^gnatpp^})
15017 on a set of project units thanks to the combination of the switches
15018 @option{-P}, @option{-U} and possibly the main unit when one is interested
15019 in its closure. For instance,
15023 will compute the metrics for all the immediate units of project
15026 gnat metric -Pproj -U
15028 will compute the metrics for all the units of the closure of projects
15029 rooted at @code{proj}.
15031 gnat metric -Pproj -U main_unit
15033 will compute the metrics for the closure of units rooted at
15034 @code{main_unit}. This last possibility relies implicitly
15035 on @command{gnatbind}'s option @option{-R}.
15037 @c **********************
15038 @node An Extended Example
15039 @section An Extended Example
15042 Suppose that we have two programs, @var{prog1} and @var{prog2},
15043 whose sources are in corresponding directories. We would like
15044 to build them with a single @command{gnatmake} command, and we want to place
15045 their object files into @file{build} subdirectories of the source directories.
15046 Furthermore, we want to have to have two separate subdirectories
15047 in @file{build} -- @file{release} and @file{debug} -- which will contain
15048 the object files compiled with different set of compilation flags.
15050 In other words, we have the following structure:
15067 Here are the project files that we must place in a directory @file{main}
15068 to maintain this structure:
15072 @item We create a @code{Common} project with a package @code{Compiler} that
15073 specifies the compilation ^switches^switches^:
15078 @b{project} Common @b{is}
15080 @b{for} Source_Dirs @b{use} (); -- No source files
15084 @b{type} Build_Type @b{is} ("release", "debug");
15085 Build : Build_Type := External ("BUILD", "debug");
15088 @b{package} Compiler @b{is}
15089 @b{case} Build @b{is}
15090 @b{when} "release" =>
15091 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
15092 @b{use} ("^-O2^-O2^");
15093 @b{when} "debug" =>
15094 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
15095 @b{use} ("^-g^-g^");
15103 @item We create separate projects for the two programs:
15110 @b{project} Prog1 @b{is}
15112 @b{for} Source_Dirs @b{use} ("prog1");
15113 @b{for} Object_Dir @b{use} "prog1/build/" & Common.Build;
15115 @b{package} Compiler @b{renames} Common.Compiler;
15126 @b{project} Prog2 @b{is}
15128 @b{for} Source_Dirs @b{use} ("prog2");
15129 @b{for} Object_Dir @b{use} "prog2/build/" & Common.Build;
15131 @b{package} Compiler @b{renames} Common.Compiler;
15137 @item We create a wrapping project @code{Main}:
15146 @b{project} Main @b{is}
15148 @b{package} Compiler @b{renames} Common.Compiler;
15154 @item Finally we need to create a dummy procedure that @code{with}s (either
15155 explicitly or implicitly) all the sources of our two programs.
15160 Now we can build the programs using the command
15163 gnatmake ^-P^/PROJECT_FILE=^main dummy
15167 for the Debug mode, or
15171 gnatmake -Pmain -XBUILD=release
15177 GNAT MAKE /PROJECT_FILE=main /EXTERNAL_REFERENCE=BUILD=release
15182 for the Release mode.
15184 @c ********************************
15185 @c * Project File Complete Syntax *
15186 @c ********************************
15188 @node Project File Complete Syntax
15189 @section Project File Complete Syntax
15193 context_clause project_declaration
15199 @b{with} path_name @{ , path_name @} ;
15204 project_declaration ::=
15205 simple_project_declaration | project_extension
15207 simple_project_declaration ::=
15208 @b{project} <project_>simple_name @b{is}
15209 @{declarative_item@}
15210 @b{end} <project_>simple_name;
15212 project_extension ::=
15213 @b{project} <project_>simple_name @b{extends} path_name @b{is}
15214 @{declarative_item@}
15215 @b{end} <project_>simple_name;
15217 declarative_item ::=
15218 package_declaration |
15219 typed_string_declaration |
15220 other_declarative_item
15222 package_declaration ::=
15223 package_spec | package_renaming
15226 @b{package} package_identifier @b{is}
15227 @{simple_declarative_item@}
15228 @b{end} package_identifier ;
15230 package_identifier ::=
15231 @code{Naming} | @code{Builder} | @code{Compiler} | @code{Binder} |
15232 @code{Linker} | @code{Finder} | @code{Cross_Reference} |
15233 @code{^gnatls^gnatls^} | @code{IDE} | @code{Pretty_Printer}
15235 package_renaming ::==
15236 @b{package} package_identifier @b{renames}
15237 <project_>simple_name.package_identifier ;
15239 typed_string_declaration ::=
15240 @b{type} <typed_string_>_simple_name @b{is}
15241 ( string_literal @{, string_literal@} );
15243 other_declarative_item ::=
15244 attribute_declaration |
15245 typed_variable_declaration |
15246 variable_declaration |
15249 attribute_declaration ::=
15250 full_associative_array_declaration |
15251 @b{for} attribute_designator @b{use} expression ;
15253 full_associative_array_declaration ::=
15254 @b{for} <associative_array_attribute_>simple_name @b{use}
15255 <project_>simple_name [ . <package_>simple_Name ] ' <attribute_>simple_name ;
15257 attribute_designator ::=
15258 <simple_attribute_>simple_name |
15259 <associative_array_attribute_>simple_name ( string_literal )
15261 typed_variable_declaration ::=
15262 <typed_variable_>simple_name : <typed_string_>name := string_expression ;
15264 variable_declaration ::=
15265 <variable_>simple_name := expression;
15275 attribute_reference
15281 ( <string_>expression @{ , <string_>expression @} )
15284 @b{external} ( string_literal [, string_literal] )
15286 attribute_reference ::=
15287 attribute_prefix ' <simple_attribute_>simple_name [ ( literal_string ) ]
15289 attribute_prefix ::=
15291 <project_>simple_name | package_identifier |
15292 <project_>simple_name . package_identifier
15294 case_construction ::=
15295 @b{case} <typed_variable_>name @b{is}
15300 @b{when} discrete_choice_list =>
15301 @{case_construction | attribute_declaration@}
15303 discrete_choice_list ::=
15304 string_literal @{| string_literal@} |
15308 simple_name @{. simple_name@}
15311 identifier (same as Ada)
15315 @node The Cross-Referencing Tools gnatxref and gnatfind
15316 @chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
15321 The compiler generates cross-referencing information (unless
15322 you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files.
15323 This information indicates where in the source each entity is declared and
15324 referenced. Note that entities in package Standard are not included, but
15325 entities in all other predefined units are included in the output.
15327 Before using any of these two tools, you need to compile successfully your
15328 application, so that GNAT gets a chance to generate the cross-referencing
15331 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
15332 information to provide the user with the capability to easily locate the
15333 declaration and references to an entity. These tools are quite similar,
15334 the difference being that @code{gnatfind} is intended for locating
15335 definitions and/or references to a specified entity or entities, whereas
15336 @code{gnatxref} is oriented to generating a full report of all
15339 To use these tools, you must not compile your application using the
15340 @option{-gnatx} switch on the @command{gnatmake} command line
15341 (@pxref{The GNAT Make Program gnatmake}). Otherwise, cross-referencing
15342 information will not be generated.
15344 Note: to invoke @code{gnatxref} or @code{gnatfind} with a project file,
15345 use the @code{gnat} driver (see @ref{The GNAT Driver and Project Files}).
15348 * gnatxref Switches::
15349 * gnatfind Switches::
15350 * Project Files for gnatxref and gnatfind::
15351 * Regular Expressions in gnatfind and gnatxref::
15352 * Examples of gnatxref Usage::
15353 * Examples of gnatfind Usage::
15356 @node gnatxref Switches
15357 @section @code{gnatxref} Switches
15360 The command invocation for @code{gnatxref} is:
15362 $ gnatxref @ovar{switches} @var{sourcefile1} @r{[}@var{sourcefile2} @dots{}@r{]}
15371 identifies the source files for which a report is to be generated. The
15372 ``with''ed units will be processed too. You must provide at least one file.
15374 These file names are considered to be regular expressions, so for instance
15375 specifying @file{source*.adb} is the same as giving every file in the current
15376 directory whose name starts with @file{source} and whose extension is
15379 You shouldn't specify any directory name, just base names. @command{gnatxref}
15380 and @command{gnatfind} will be able to locate these files by themselves using
15381 the source path. If you specify directories, no result is produced.
15386 The switches can be:
15390 @cindex @option{--version} @command{gnatxref}
15391 Display Copyright and version, then exit disregarding all other options.
15394 @cindex @option{--help} @command{gnatxref}
15395 If @option{--version} was not used, display usage, then exit disregarding
15398 @item ^-a^/ALL_FILES^
15399 @cindex @option{^-a^/ALL_FILES^} (@command{gnatxref})
15400 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15401 the read-only files found in the library search path. Otherwise, these files
15402 will be ignored. This option can be used to protect Gnat sources or your own
15403 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15404 much faster, and their output much smaller. Read-only here refers to access
15405 or permissions status in the file system for the current user.
15408 @cindex @option{-aIDIR} (@command{gnatxref})
15409 When looking for source files also look in directory DIR. The order in which
15410 source file search is undertaken is the same as for @command{gnatmake}.
15413 @cindex @option{-aODIR} (@command{gnatxref})
15414 When searching for library and object files, look in directory
15415 DIR. The order in which library files are searched is the same as for
15416 @command{gnatmake}.
15419 @cindex @option{-nostdinc} (@command{gnatxref})
15420 Do not look for sources in the system default directory.
15423 @cindex @option{-nostdlib} (@command{gnatxref})
15424 Do not look for library files in the system default directory.
15426 @item --RTS=@var{rts-path}
15427 @cindex @option{--RTS} (@command{gnatxref})
15428 Specifies the default location of the runtime library. Same meaning as the
15429 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15431 @item ^-d^/DERIVED_TYPES^
15432 @cindex @option{^-d^/DERIVED_TYPES^} (@command{gnatxref})
15433 If this switch is set @code{gnatxref} will output the parent type
15434 reference for each matching derived types.
15436 @item ^-f^/FULL_PATHNAME^
15437 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatxref})
15438 If this switch is set, the output file names will be preceded by their
15439 directory (if the file was found in the search path). If this switch is
15440 not set, the directory will not be printed.
15442 @item ^-g^/IGNORE_LOCALS^
15443 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatxref})
15444 If this switch is set, information is output only for library-level
15445 entities, ignoring local entities. The use of this switch may accelerate
15446 @code{gnatfind} and @code{gnatxref}.
15449 @cindex @option{-IDIR} (@command{gnatxref})
15450 Equivalent to @samp{-aODIR -aIDIR}.
15453 @cindex @option{-pFILE} (@command{gnatxref})
15454 Specify a project file to use @xref{Project Files}.
15455 If you need to use the @file{.gpr}
15456 project files, you should use gnatxref through the GNAT driver
15457 (@command{gnat xref -Pproject}).
15459 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15460 project file in the current directory.
15462 If a project file is either specified or found by the tools, then the content
15463 of the source directory and object directory lines are added as if they
15464 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^}
15465 and @samp{^-aO^OBJECT_SEARCH^}.
15467 Output only unused symbols. This may be really useful if you give your
15468 main compilation unit on the command line, as @code{gnatxref} will then
15469 display every unused entity and 'with'ed package.
15473 Instead of producing the default output, @code{gnatxref} will generate a
15474 @file{tags} file that can be used by vi. For examples how to use this
15475 feature, see @ref{Examples of gnatxref Usage}. The tags file is output
15476 to the standard output, thus you will have to redirect it to a file.
15482 All these switches may be in any order on the command line, and may even
15483 appear after the file names. They need not be separated by spaces, thus
15484 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15485 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15487 @node gnatfind Switches
15488 @section @code{gnatfind} Switches
15491 The command line for @code{gnatfind} is:
15494 $ gnatfind @ovar{switches} @var{pattern}@r{[}:@var{sourcefile}@r{[}:@var{line}@r{[}:@var{column}@r{]]]}
15495 @r{[}@var{file1} @var{file2} @dots{}]
15503 An entity will be output only if it matches the regular expression found
15504 in @var{pattern}, see @ref{Regular Expressions in gnatfind and gnatxref}.
15506 Omitting the pattern is equivalent to specifying @samp{*}, which
15507 will match any entity. Note that if you do not provide a pattern, you
15508 have to provide both a sourcefile and a line.
15510 Entity names are given in Latin-1, with uppercase/lowercase equivalence
15511 for matching purposes. At the current time there is no support for
15512 8-bit codes other than Latin-1, or for wide characters in identifiers.
15515 @code{gnatfind} will look for references, bodies or declarations
15516 of symbols referenced in @file{@var{sourcefile}}, at line @var{line}
15517 and column @var{column}. See @ref{Examples of gnatfind Usage}
15518 for syntax examples.
15521 is a decimal integer identifying the line number containing
15522 the reference to the entity (or entities) to be located.
15525 is a decimal integer identifying the exact location on the
15526 line of the first character of the identifier for the
15527 entity reference. Columns are numbered from 1.
15529 @item file1 file2 @dots{}
15530 The search will be restricted to these source files. If none are given, then
15531 the search will be done for every library file in the search path.
15532 These file must appear only after the pattern or sourcefile.
15534 These file names are considered to be regular expressions, so for instance
15535 specifying @file{source*.adb} is the same as giving every file in the current
15536 directory whose name starts with @file{source} and whose extension is
15539 The location of the spec of the entity will always be displayed, even if it
15540 isn't in one of @file{@var{file1}}, @file{@var{file2}},@enddots{} The
15541 occurrences of the entity in the separate units of the ones given on the
15542 command line will also be displayed.
15544 Note that if you specify at least one file in this part, @code{gnatfind} may
15545 sometimes not be able to find the body of the subprograms.
15550 At least one of 'sourcefile' or 'pattern' has to be present on
15553 The following switches are available:
15557 @cindex @option{--version} @command{gnatfind}
15558 Display Copyright and version, then exit disregarding all other options.
15561 @cindex @option{--help} @command{gnatfind}
15562 If @option{--version} was not used, display usage, then exit disregarding
15565 @item ^-a^/ALL_FILES^
15566 @cindex @option{^-a^/ALL_FILES^} (@command{gnatfind})
15567 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15568 the read-only files found in the library search path. Otherwise, these files
15569 will be ignored. This option can be used to protect Gnat sources or your own
15570 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15571 much faster, and their output much smaller. Read-only here refers to access
15572 or permission status in the file system for the current user.
15575 @cindex @option{-aIDIR} (@command{gnatfind})
15576 When looking for source files also look in directory DIR. The order in which
15577 source file search is undertaken is the same as for @command{gnatmake}.
15580 @cindex @option{-aODIR} (@command{gnatfind})
15581 When searching for library and object files, look in directory
15582 DIR. The order in which library files are searched is the same as for
15583 @command{gnatmake}.
15586 @cindex @option{-nostdinc} (@command{gnatfind})
15587 Do not look for sources in the system default directory.
15590 @cindex @option{-nostdlib} (@command{gnatfind})
15591 Do not look for library files in the system default directory.
15593 @item --ext=@var{extension}
15594 @cindex @option{--ext} (@command{gnatfind})
15595 Specify an alternate ali file extension. The default is @code{ali} and other
15596 extensions (e.g. @code{sli} for SPARK library files) may be specified via this
15597 switch. Note that if this switch overrides the default, which means that only
15598 the new extension will be considered.
15600 @item --RTS=@var{rts-path}
15601 @cindex @option{--RTS} (@command{gnatfind})
15602 Specifies the default location of the runtime library. Same meaning as the
15603 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15605 @item ^-d^/DERIVED_TYPE_INFORMATION^
15606 @cindex @option{^-d^/DERIVED_TYPE_INFORMATION^} (@code{gnatfind})
15607 If this switch is set, then @code{gnatfind} will output the parent type
15608 reference for each matching derived types.
15610 @item ^-e^/EXPRESSIONS^
15611 @cindex @option{^-e^/EXPRESSIONS^} (@command{gnatfind})
15612 By default, @code{gnatfind} accept the simple regular expression set for
15613 @samp{pattern}. If this switch is set, then the pattern will be
15614 considered as full Unix-style regular expression.
15616 @item ^-f^/FULL_PATHNAME^
15617 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatfind})
15618 If this switch is set, the output file names will be preceded by their
15619 directory (if the file was found in the search path). If this switch is
15620 not set, the directory will not be printed.
15622 @item ^-g^/IGNORE_LOCALS^
15623 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatfind})
15624 If this switch is set, information is output only for library-level
15625 entities, ignoring local entities. The use of this switch may accelerate
15626 @code{gnatfind} and @code{gnatxref}.
15629 @cindex @option{-IDIR} (@command{gnatfind})
15630 Equivalent to @samp{-aODIR -aIDIR}.
15633 @cindex @option{-pFILE} (@command{gnatfind})
15634 Specify a project file (@pxref{Project Files}) to use.
15635 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15636 project file in the current directory.
15638 If a project file is either specified or found by the tools, then the content
15639 of the source directory and object directory lines are added as if they
15640 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^} and
15641 @samp{^-aO^/OBJECT_SEARCH^}.
15643 @item ^-r^/REFERENCES^
15644 @cindex @option{^-r^/REFERENCES^} (@command{gnatfind})
15645 By default, @code{gnatfind} will output only the information about the
15646 declaration, body or type completion of the entities. If this switch is
15647 set, the @code{gnatfind} will locate every reference to the entities in
15648 the files specified on the command line (or in every file in the search
15649 path if no file is given on the command line).
15651 @item ^-s^/PRINT_LINES^
15652 @cindex @option{^-s^/PRINT_LINES^} (@command{gnatfind})
15653 If this switch is set, then @code{gnatfind} will output the content
15654 of the Ada source file lines were the entity was found.
15656 @item ^-t^/TYPE_HIERARCHY^
15657 @cindex @option{^-t^/TYPE_HIERARCHY^} (@command{gnatfind})
15658 If this switch is set, then @code{gnatfind} will output the type hierarchy for
15659 the specified type. It act like -d option but recursively from parent
15660 type to parent type. When this switch is set it is not possible to
15661 specify more than one file.
15666 All these switches may be in any order on the command line, and may even
15667 appear after the file names. They need not be separated by spaces, thus
15668 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15669 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15671 As stated previously, gnatfind will search in every directory in the
15672 search path. You can force it to look only in the current directory if
15673 you specify @code{*} at the end of the command line.
15675 @node Project Files for gnatxref and gnatfind
15676 @section Project Files for @command{gnatxref} and @command{gnatfind}
15679 Project files allow a programmer to specify how to compile its
15680 application, where to find sources, etc. These files are used
15682 primarily by GPS, but they can also be used
15685 @code{gnatxref} and @code{gnatfind}.
15687 A project file name must end with @file{.gpr}. If a single one is
15688 present in the current directory, then @code{gnatxref} and @code{gnatfind} will
15689 extract the information from it. If multiple project files are found, none of
15690 them is read, and you have to use the @samp{-p} switch to specify the one
15693 The following lines can be included, even though most of them have default
15694 values which can be used in most cases.
15695 The lines can be entered in any order in the file.
15696 Except for @file{src_dir} and @file{obj_dir}, you can only have one instance of
15697 each line. If you have multiple instances, only the last one is taken into
15702 [default: @code{"^./^[]^"}]
15703 specifies a directory where to look for source files. Multiple @code{src_dir}
15704 lines can be specified and they will be searched in the order they
15708 [default: @code{"^./^[]^"}]
15709 specifies a directory where to look for object and library files. Multiple
15710 @code{obj_dir} lines can be specified, and they will be searched in the order
15713 @item comp_opt=SWITCHES
15714 [default: @code{""}]
15715 creates a variable which can be referred to subsequently by using
15716 the @code{$@{comp_opt@}} notation. This is intended to store the default
15717 switches given to @command{gnatmake} and @command{gcc}.
15719 @item bind_opt=SWITCHES
15720 [default: @code{""}]
15721 creates a variable which can be referred to subsequently by using
15722 the @samp{$@{bind_opt@}} notation. This is intended to store the default
15723 switches given to @command{gnatbind}.
15725 @item link_opt=SWITCHES
15726 [default: @code{""}]
15727 creates a variable which can be referred to subsequently by using
15728 the @samp{$@{link_opt@}} notation. This is intended to store the default
15729 switches given to @command{gnatlink}.
15731 @item main=EXECUTABLE
15732 [default: @code{""}]
15733 specifies the name of the executable for the application. This variable can
15734 be referred to in the following lines by using the @samp{$@{main@}} notation.
15737 @item comp_cmd=COMMAND
15738 [default: @code{"GNAT COMPILE /SEARCH=$@{src_dir@} /DEBUG /TRY_SEMANTICS"}]
15741 @item comp_cmd=COMMAND
15742 [default: @code{"gcc -c -I$@{src_dir@} -g -gnatq"}]
15744 specifies the command used to compile a single file in the application.
15747 @item make_cmd=COMMAND
15748 [default: @code{"GNAT MAKE $@{main@}
15749 /SOURCE_SEARCH=$@{src_dir@} /OBJECT_SEARCH=$@{obj_dir@}
15750 /DEBUG /TRY_SEMANTICS /COMPILER_QUALIFIERS $@{comp_opt@}
15751 /BINDER_QUALIFIERS $@{bind_opt@} /LINKER_QUALIFIERS $@{link_opt@}"}]
15754 @item make_cmd=COMMAND
15755 [default: @code{"gnatmake $@{main@} -aI$@{src_dir@}
15756 -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@}
15757 -bargs $@{bind_opt@} -largs $@{link_opt@}"}]
15759 specifies the command used to recompile the whole application.
15761 @item run_cmd=COMMAND
15762 [default: @code{"$@{main@}"}]
15763 specifies the command used to run the application.
15765 @item debug_cmd=COMMAND
15766 [default: @code{"gdb $@{main@}"}]
15767 specifies the command used to debug the application
15772 @command{gnatxref} and @command{gnatfind} only take into account the
15773 @code{src_dir} and @code{obj_dir} lines, and ignore the others.
15775 @node Regular Expressions in gnatfind and gnatxref
15776 @section Regular Expressions in @code{gnatfind} and @code{gnatxref}
15779 As specified in the section about @command{gnatfind}, the pattern can be a
15780 regular expression. Actually, there are to set of regular expressions
15781 which are recognized by the program:
15784 @item globbing patterns
15785 These are the most usual regular expression. They are the same that you
15786 generally used in a Unix shell command line, or in a DOS session.
15788 Here is a more formal grammar:
15795 term ::= elmt -- matches elmt
15796 term ::= elmt elmt -- concatenation (elmt then elmt)
15797 term ::= * -- any string of 0 or more characters
15798 term ::= ? -- matches any character
15799 term ::= [char @{char@}] -- matches any character listed
15800 term ::= [char - char] -- matches any character in range
15804 @item full regular expression
15805 The second set of regular expressions is much more powerful. This is the
15806 type of regular expressions recognized by utilities such a @file{grep}.
15808 The following is the form of a regular expression, expressed in Ada
15809 reference manual style BNF is as follows
15816 regexp ::= term @{| term@} -- alternation (term or term @dots{})
15818 term ::= item @{item@} -- concatenation (item then item)
15820 item ::= elmt -- match elmt
15821 item ::= elmt * -- zero or more elmt's
15822 item ::= elmt + -- one or more elmt's
15823 item ::= elmt ? -- matches elmt or nothing
15826 elmt ::= nschar -- matches given character
15827 elmt ::= [nschar @{nschar@}] -- matches any character listed
15828 elmt ::= [^^^ nschar @{nschar@}] -- matches any character not listed
15829 elmt ::= [char - char] -- matches chars in given range
15830 elmt ::= \ char -- matches given character
15831 elmt ::= . -- matches any single character
15832 elmt ::= ( regexp ) -- parens used for grouping
15834 char ::= any character, including special characters
15835 nschar ::= any character except ()[].*+?^^^
15839 Following are a few examples:
15843 will match any of the two strings @samp{abcde} and @samp{fghi},
15846 will match any string like @samp{abd}, @samp{abcd}, @samp{abccd},
15847 @samp{abcccd}, and so on,
15850 will match any string which has only lowercase characters in it (and at
15851 least one character.
15856 @node Examples of gnatxref Usage
15857 @section Examples of @code{gnatxref} Usage
15859 @subsection General Usage
15862 For the following examples, we will consider the following units:
15864 @smallexample @c ada
15870 3: procedure Foo (B : in Integer);
15877 1: package body Main is
15878 2: procedure Foo (B : in Integer) is
15889 2: procedure Print (B : Integer);
15898 The first thing to do is to recompile your application (for instance, in
15899 that case just by doing a @samp{gnatmake main}, so that GNAT generates
15900 the cross-referencing information.
15901 You can then issue any of the following commands:
15903 @item gnatxref main.adb
15904 @code{gnatxref} generates cross-reference information for main.adb
15905 and every unit 'with'ed by main.adb.
15907 The output would be:
15915 Decl: main.ads 3:20
15916 Body: main.adb 2:20
15917 Ref: main.adb 4:13 5:13 6:19
15920 Ref: main.adb 6:8 7:8
15930 Decl: main.ads 3:15
15931 Body: main.adb 2:15
15934 Body: main.adb 1:14
15937 Ref: main.adb 6:12 7:12
15941 that is the entity @code{Main} is declared in main.ads, line 2, column 9,
15942 its body is in main.adb, line 1, column 14 and is not referenced any where.
15944 The entity @code{Print} is declared in bar.ads, line 2, column 15 and it
15945 it referenced in main.adb, line 6 column 12 and line 7 column 12.
15947 @item gnatxref package1.adb package2.ads
15948 @code{gnatxref} will generates cross-reference information for
15949 package1.adb, package2.ads and any other package 'with'ed by any
15955 @subsection Using gnatxref with vi
15957 @code{gnatxref} can generate a tags file output, which can be used
15958 directly from @command{vi}. Note that the standard version of @command{vi}
15959 will not work properly with overloaded symbols. Consider using another
15960 free implementation of @command{vi}, such as @command{vim}.
15963 $ gnatxref -v gnatfind.adb > tags
15967 will generate the tags file for @code{gnatfind} itself (if the sources
15968 are in the search path!).
15970 From @command{vi}, you can then use the command @samp{:tag @var{entity}}
15971 (replacing @var{entity} by whatever you are looking for), and vi will
15972 display a new file with the corresponding declaration of entity.
15975 @node Examples of gnatfind Usage
15976 @section Examples of @code{gnatfind} Usage
15980 @item gnatfind ^-f^/FULL_PATHNAME^ xyz:main.adb
15981 Find declarations for all entities xyz referenced at least once in
15982 main.adb. The references are search in every library file in the search
15985 The directories will be printed as well (as the @samp{^-f^/FULL_PATHNAME^}
15988 The output will look like:
15990 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
15991 ^directory/^[directory]^main.adb:24:10: xyz <= body
15992 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
15996 that is to say, one of the entities xyz found in main.adb is declared at
15997 line 12 of main.ads (and its body is in main.adb), and another one is
15998 declared at line 45 of foo.ads
16000 @item gnatfind ^-fs^/FULL_PATHNAME/SOURCE_LINE^ xyz:main.adb
16001 This is the same command as the previous one, instead @code{gnatfind} will
16002 display the content of the Ada source file lines.
16004 The output will look like:
16007 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
16009 ^directory/^[directory]^main.adb:24:10: xyz <= body
16011 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
16016 This can make it easier to find exactly the location your are looking
16019 @item gnatfind ^-r^/REFERENCES^ "*x*":main.ads:123 foo.adb
16020 Find references to all entities containing an x that are
16021 referenced on line 123 of main.ads.
16022 The references will be searched only in main.ads and foo.adb.
16024 @item gnatfind main.ads:123
16025 Find declarations and bodies for all entities that are referenced on
16026 line 123 of main.ads.
16028 This is the same as @code{gnatfind "*":main.adb:123}.
16030 @item gnatfind ^mydir/^[mydir]^main.adb:123:45
16031 Find the declaration for the entity referenced at column 45 in
16032 line 123 of file main.adb in directory mydir. Note that it
16033 is usual to omit the identifier name when the column is given,
16034 since the column position identifies a unique reference.
16036 The column has to be the beginning of the identifier, and should not
16037 point to any character in the middle of the identifier.
16041 @c *********************************
16042 @node The GNAT Pretty-Printer gnatpp
16043 @chapter The GNAT Pretty-Printer @command{gnatpp}
16045 @cindex Pretty-Printer
16048 ^The @command{gnatpp} tool^GNAT PRETTY^ is an ASIS-based utility
16049 for source reformatting / pretty-printing.
16050 It takes an Ada source file as input and generates a reformatted
16052 You can specify various style directives via switches; e.g.,
16053 identifier case conventions, rules of indentation, and comment layout.
16055 To produce a reformatted file, @command{gnatpp} generates and uses the ASIS
16056 tree for the input source and thus requires the input to be syntactically and
16057 semantically legal.
16058 If this condition is not met, @command{gnatpp} will terminate with an
16059 error message; no output file will be generated.
16061 If the source files presented to @command{gnatpp} contain
16062 preprocessing directives, then the output file will
16063 correspond to the generated source after all
16064 preprocessing is carried out. There is no way
16065 using @command{gnatpp} to obtain pretty printed files that
16066 include the preprocessing directives.
16068 If the compilation unit
16069 contained in the input source depends semantically upon units located
16070 outside the current directory, you have to provide the source search path
16071 when invoking @command{gnatpp}, if these units are contained in files with
16072 names that do not follow the GNAT file naming rules, you have to provide
16073 the configuration file describing the corresponding naming scheme;
16074 see the description of the @command{gnatpp}
16075 switches below. Another possibility is to use a project file and to
16076 call @command{gnatpp} through the @command{gnat} driver
16078 The @command{gnatpp} command has the form
16081 $ gnatpp @ovar{switches} @var{filename}
16088 @var{switches} is an optional sequence of switches defining such properties as
16089 the formatting rules, the source search path, and the destination for the
16093 @var{filename} is the name (including the extension) of the source file to
16094 reformat; ``wildcards'' or several file names on the same gnatpp command are
16095 allowed. The file name may contain path information; it does not have to
16096 follow the GNAT file naming rules
16100 * Switches for gnatpp::
16101 * Formatting Rules::
16104 @node Switches for gnatpp
16105 @section Switches for @command{gnatpp}
16108 The following subsections describe the various switches accepted by
16109 @command{gnatpp}, organized by category.
16112 You specify a switch by supplying a name and generally also a value.
16113 In many cases the values for a switch with a given name are incompatible with
16115 (for example the switch that controls the casing of a reserved word may have
16116 exactly one value: upper case, lower case, or
16117 mixed case) and thus exactly one such switch can be in effect for an
16118 invocation of @command{gnatpp}.
16119 If more than one is supplied, the last one is used.
16120 However, some values for the same switch are mutually compatible.
16121 You may supply several such switches to @command{gnatpp}, but then
16122 each must be specified in full, with both the name and the value.
16123 Abbreviated forms (the name appearing once, followed by each value) are
16125 For example, to set
16126 the alignment of the assignment delimiter both in declarations and in
16127 assignment statements, you must write @option{-A2A3}
16128 (or @option{-A2 -A3}), but not @option{-A23}.
16132 In many cases the set of options for a given qualifier are incompatible with
16133 each other (for example the qualifier that controls the casing of a reserved
16134 word may have exactly one option, which specifies either upper case, lower
16135 case, or mixed case), and thus exactly one such option can be in effect for
16136 an invocation of @command{gnatpp}.
16137 If more than one is supplied, the last one is used.
16138 However, some qualifiers have options that are mutually compatible,
16139 and then you may then supply several such options when invoking
16143 In most cases, it is obvious whether or not the
16144 ^values for a switch with a given name^options for a given qualifier^
16145 are compatible with each other.
16146 When the semantics might not be evident, the summaries below explicitly
16147 indicate the effect.
16150 * Alignment Control::
16152 * Construct Layout Control::
16153 * General Text Layout Control::
16154 * Other Formatting Options::
16155 * Setting the Source Search Path::
16156 * Output File Control::
16157 * Other gnatpp Switches::
16160 @node Alignment Control
16161 @subsection Alignment Control
16162 @cindex Alignment control in @command{gnatpp}
16165 Programs can be easier to read if certain constructs are vertically aligned.
16166 By default all alignments are set ON.
16167 Through the @option{^-A0^/ALIGN=OFF^} switch you may reset the default to
16168 OFF, and then use one or more of the other
16169 ^@option{-A@var{n}} switches^@option{/ALIGN} options^
16170 to activate alignment for specific constructs.
16173 @cindex @option{^-A@var{n}^/ALIGN^} (@command{gnatpp})
16177 Set all alignments to ON
16180 @item ^-A0^/ALIGN=OFF^
16181 Set all alignments to OFF
16183 @item ^-A1^/ALIGN=COLONS^
16184 Align @code{:} in declarations
16186 @item ^-A2^/ALIGN=DECLARATIONS^
16187 Align @code{:=} in initializations in declarations
16189 @item ^-A3^/ALIGN=STATEMENTS^
16190 Align @code{:=} in assignment statements
16192 @item ^-A4^/ALIGN=ARROWS^
16193 Align @code{=>} in associations
16195 @item ^-A5^/ALIGN=COMPONENT_CLAUSES^
16196 Align @code{at} keywords in the component clauses in record
16197 representation clauses
16201 The @option{^-A^/ALIGN^} switches are mutually compatible; any combination
16204 @node Casing Control
16205 @subsection Casing Control
16206 @cindex Casing control in @command{gnatpp}
16209 @command{gnatpp} allows you to specify the casing for reserved words,
16210 pragma names, attribute designators and identifiers.
16211 For identifiers you may define a
16212 general rule for name casing but also override this rule
16213 via a set of dictionary files.
16215 Three types of casing are supported: lower case, upper case, and mixed case.
16216 Lower and upper case are self-explanatory (but since some letters in
16217 Latin1 and other GNAT-supported character sets
16218 exist only in lower-case form, an upper case conversion will have no
16220 ``Mixed case'' means that the first letter, and also each letter immediately
16221 following an underscore, are converted to their uppercase forms;
16222 all the other letters are converted to their lowercase forms.
16225 @cindex @option{^-a@var{x}^/ATTRIBUTE^} (@command{gnatpp})
16226 @item ^-aL^/ATTRIBUTE_CASING=LOWER_CASE^
16227 Attribute designators are lower case
16229 @item ^-aU^/ATTRIBUTE_CASING=UPPER_CASE^
16230 Attribute designators are upper case
16232 @item ^-aM^/ATTRIBUTE_CASING=MIXED_CASE^
16233 Attribute designators are mixed case (this is the default)
16235 @cindex @option{^-k@var{x}^/KEYWORD_CASING^} (@command{gnatpp})
16236 @item ^-kL^/KEYWORD_CASING=LOWER_CASE^
16237 Keywords (technically, these are known in Ada as @emph{reserved words}) are
16238 lower case (this is the default)
16240 @item ^-kU^/KEYWORD_CASING=UPPER_CASE^
16241 Keywords are upper case
16243 @cindex @option{^-n@var{x}^/NAME_CASING^} (@command{gnatpp})
16244 @item ^-nD^/NAME_CASING=AS_DECLARED^
16245 Name casing for defining occurrences are as they appear in the source file
16246 (this is the default)
16248 @item ^-nU^/NAME_CASING=UPPER_CASE^
16249 Names are in upper case
16251 @item ^-nL^/NAME_CASING=LOWER_CASE^
16252 Names are in lower case
16254 @item ^-nM^/NAME_CASING=MIXED_CASE^
16255 Names are in mixed case
16257 @cindex @option{^-p@var{x}^/PRAGMA_CASING^} (@command{gnatpp})
16258 @item ^-pL^/PRAGMA_CASING=LOWER_CASE^
16259 Pragma names are lower case
16261 @item ^-pU^/PRAGMA_CASING=UPPER_CASE^
16262 Pragma names are upper case
16264 @item ^-pM^/PRAGMA_CASING=MIXED_CASE^
16265 Pragma names are mixed case (this is the default)
16267 @item ^-D@var{file}^/DICTIONARY=@var{file}^
16268 @cindex @option{^-D^/DICTIONARY^} (@command{gnatpp})
16269 Use @var{file} as a @emph{dictionary file} that defines
16270 the casing for a set of specified names,
16271 thereby overriding the effect on these names by
16272 any explicit or implicit
16273 ^-n^/NAME_CASING^ switch.
16274 To supply more than one dictionary file,
16275 use ^several @option{-D} switches^a list of files as options^.
16278 @option{gnatpp} implicitly uses a @emph{default dictionary file}
16279 to define the casing for the Ada predefined names and
16280 the names declared in the GNAT libraries.
16282 @item ^-D-^/SPECIFIC_CASING^
16283 @cindex @option{^-D-^/SPECIFIC_CASING^} (@command{gnatpp})
16284 Do not use the default dictionary file;
16285 instead, use the casing
16286 defined by a @option{^-n^/NAME_CASING^} switch and any explicit
16291 The structure of a dictionary file, and details on the conventions
16292 used in the default dictionary file, are defined in @ref{Name Casing}.
16294 The @option{^-D-^/SPECIFIC_CASING^} and
16295 @option{^-D@var{file}^/DICTIONARY=@var{file}^} switches are mutually
16298 @node Construct Layout Control
16299 @subsection Construct Layout Control
16300 @cindex Layout control in @command{gnatpp}
16303 This group of @command{gnatpp} switches controls the layout of comments and
16304 complex syntactic constructs. See @ref{Formatting Comments} for details
16308 @cindex @option{^-c@var{n}^/COMMENTS_LAYOUT^} (@command{gnatpp})
16309 @item ^-c0^/COMMENTS_LAYOUT=UNTOUCHED^
16310 All the comments remain unchanged
16312 @item ^-c1^/COMMENTS_LAYOUT=DEFAULT^
16313 GNAT-style comment line indentation (this is the default).
16315 @item ^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^
16316 Reference-manual comment line indentation.
16318 @item ^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^
16319 GNAT-style comment beginning
16321 @item ^-c4^/COMMENTS_LAYOUT=REFORMAT^
16322 Reformat comment blocks
16324 @item ^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^
16325 Keep unchanged special form comments
16327 Reformat comment blocks
16329 @cindex @option{^-l@var{n}^/CONSTRUCT_LAYOUT^} (@command{gnatpp})
16330 @item ^-l1^/CONSTRUCT_LAYOUT=GNAT^
16331 GNAT-style layout (this is the default)
16333 @item ^-l2^/CONSTRUCT_LAYOUT=COMPACT^
16336 @item ^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^
16339 @cindex @option{^-N^/NOTABS^} (@command{gnatpp})
16341 All the VT characters are removed from the comment text. All the HT characters
16342 are expanded with the sequences of space characters to get to the next tab
16345 @cindex @option{^--no-separate-is^/NO_SEPARATE_IS^} (@command{gnatpp})
16346 @item ^--no-separate-is^/NO_SEPARATE_IS^
16347 Do not place the keyword @code{is} on a separate line in a subprogram body in
16348 case if the spec occupies more then one line.
16350 @cindex @option{^--separate-label^/SEPARATE_LABEL^} (@command{gnatpp})
16351 @item ^--separate-label^/SEPARATE_LABEL^
16352 Place statement label(s) on a separate line, with the following statement
16355 @cindex @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} (@command{gnatpp})
16356 @item ^--separate-loop-then^/SEPARATE_LOOP_THEN^
16357 Place the keyword @code{loop} in FOR and WHILE loop statements and the
16358 keyword @code{then} in IF statements on a separate line.
16360 @cindex @option{^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^} (@command{gnatpp})
16361 @item ^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^
16362 Do not place the keyword @code{loop} in FOR and WHILE loop statements and the
16363 keyword @code{then} in IF statements on a separate line. This option is
16364 incompatible with @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} option.
16366 @cindex @option{^--use-on-new-line^/USE_ON_NEW_LINE^} (@command{gnatpp})
16367 @item ^--use-on-new-line^/USE_ON_NEW_LINE^
16368 Start each USE clause in a context clause from a separate line.
16370 @cindex @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^} (@command{gnatpp})
16371 @item ^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^
16372 Use a separate line for a loop or block statement name, but do not use an extra
16373 indentation level for the statement itself.
16379 The @option{-c1} and @option{-c2} switches are incompatible.
16380 The @option{-c3} and @option{-c4} switches are compatible with each other and
16381 also with @option{-c1} and @option{-c2}. The @option{-c0} switch disables all
16382 the other comment formatting switches.
16384 The @option{-l1}, @option{-l2}, and @option{-l3} switches are incompatible.
16389 For the @option{/COMMENTS_LAYOUT} qualifier:
16392 The @option{DEFAULT} and @option{STANDARD_INDENT} options are incompatible.
16394 The @option{GNAT_BEGINNING} and @option{REFORMAT} options are compatible with
16395 each other and also with @option{DEFAULT} and @option{STANDARD_INDENT}.
16399 The @option{GNAT}, @option{COMPACT}, and @option{UNCOMPACT} options for the
16400 @option{/CONSTRUCT_LAYOUT} qualifier are incompatible.
16403 @node General Text Layout Control
16404 @subsection General Text Layout Control
16407 These switches allow control over line length and indentation.
16410 @item ^-M@var{nnn}^/LINE_LENGTH_MAX=@var{nnn}^
16411 @cindex @option{^-M^/LINE_LENGTH^} (@command{gnatpp})
16412 Maximum line length, @var{nnn} from 32@dots{}256, the default value is 79
16414 @item ^-i@var{nnn}^/INDENTATION_LEVEL=@var{nnn}^
16415 @cindex @option{^-i^/INDENTATION_LEVEL^} (@command{gnatpp})
16416 Indentation level, @var{nnn} from 1@dots{}9, the default value is 3
16418 @item ^-cl@var{nnn}^/CONTINUATION_INDENT=@var{nnn}^
16419 @cindex @option{^-cl^/CONTINUATION_INDENT^} (@command{gnatpp})
16420 Indentation level for continuation lines (relative to the line being
16421 continued), @var{nnn} from 1@dots{}9.
16423 value is one less then the (normal) indentation level, unless the
16424 indentation is set to 1 (in which case the default value for continuation
16425 line indentation is also 1)
16428 @node Other Formatting Options
16429 @subsection Other Formatting Options
16432 These switches control the inclusion of missing end/exit labels, and
16433 the indentation level in @b{case} statements.
16436 @item ^-e^/NO_MISSED_LABELS^
16437 @cindex @option{^-e^/NO_MISSED_LABELS^} (@command{gnatpp})
16438 Do not insert missing end/exit labels. An end label is the name of
16439 a construct that may optionally be repeated at the end of the
16440 construct's declaration;
16441 e.g., the names of packages, subprograms, and tasks.
16442 An exit label is the name of a loop that may appear as target
16443 of an exit statement within the loop.
16444 By default, @command{gnatpp} inserts these end/exit labels when
16445 they are absent from the original source. This option suppresses such
16446 insertion, so that the formatted source reflects the original.
16448 @item ^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^
16449 @cindex @option{^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^} (@command{gnatpp})
16450 Insert a Form Feed character after a pragma Page.
16452 @item ^-T@var{nnn}^/MAX_INDENT=@var{nnn}^
16453 @cindex @option{^-T^/MAX_INDENT^} (@command{gnatpp})
16454 Do not use an additional indentation level for @b{case} alternatives
16455 and variants if there are @var{nnn} or more (the default
16457 If @var{nnn} is 0, an additional indentation level is
16458 used for @b{case} alternatives and variants regardless of their number.
16461 @node Setting the Source Search Path
16462 @subsection Setting the Source Search Path
16465 To define the search path for the input source file, @command{gnatpp}
16466 uses the same switches as the GNAT compiler, with the same effects.
16469 @item ^-I^/SEARCH=^@var{dir}
16470 @cindex @option{^-I^/SEARCH^} (@code{gnatpp})
16471 The same as the corresponding gcc switch
16473 @item ^-I-^/NOCURRENT_DIRECTORY^
16474 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatpp})
16475 The same as the corresponding gcc switch
16477 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE^=@var{path}
16478 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@code{gnatpp})
16479 The same as the corresponding gcc switch
16481 @item ^--RTS^/RUNTIME_SYSTEM^=@var{path}
16482 @cindex @option{^--RTS^/RUNTIME_SYSTEM^} (@code{gnatpp})
16483 The same as the corresponding gcc switch
16487 @node Output File Control
16488 @subsection Output File Control
16491 By default the output is sent to the file whose name is obtained by appending
16492 the ^@file{.pp}^@file{$PP}^ suffix to the name of the input file
16493 (if the file with this name already exists, it is unconditionally overwritten).
16494 Thus if the input file is @file{^my_ada_proc.adb^MY_ADA_PROC.ADB^} then
16495 @command{gnatpp} will produce @file{^my_ada_proc.adb.pp^MY_ADA_PROC.ADB$PP^}
16497 The output may be redirected by the following switches:
16500 @item ^-pipe^/STANDARD_OUTPUT^
16501 @cindex @option{^-pipe^/STANDARD_OUTPUT^} (@code{gnatpp})
16502 Send the output to @code{Standard_Output}
16504 @item ^-o @var{output_file}^/OUTPUT=@var{output_file}^
16505 @cindex @option{^-o^/OUTPUT^} (@code{gnatpp})
16506 Write the output into @var{output_file}.
16507 If @var{output_file} already exists, @command{gnatpp} terminates without
16508 reading or processing the input file.
16510 @item ^-of ^/FORCED_OUTPUT=^@var{output_file}
16511 @cindex @option{^-of^/FORCED_OUTPUT^} (@code{gnatpp})
16512 Write the output into @var{output_file}, overwriting the existing file
16513 (if one is present).
16515 @item ^-r^/REPLACE^
16516 @cindex @option{^-r^/REPLACE^} (@code{gnatpp})
16517 Replace the input source file with the reformatted output, and copy the
16518 original input source into the file whose name is obtained by appending the
16519 ^@file{.npp}^@file{$NPP}^ suffix to the name of the input file.
16520 If a file with this name already exists, @command{gnatpp} terminates without
16521 reading or processing the input file.
16523 @item ^-rf^/OVERRIDING_REPLACE^
16524 @cindex @option{^-rf^/OVERRIDING_REPLACE^} (@code{gnatpp})
16525 Like @option{^-r^/REPLACE^} except that if the file with the specified name
16526 already exists, it is overwritten.
16528 @item ^-rnb^/REPLACE_NO_BACKUP^
16529 @cindex @option{^-rnb^/REPLACE_NO_BACKUP^} (@code{gnatpp})
16530 Replace the input source file with the reformatted output without
16531 creating any backup copy of the input source.
16533 @item ^--eol=@var{xxx}^/END_OF_LINE=@var{xxx}^
16534 @cindex @option{^--eol^/END_OF_LINE^} (@code{gnatpp})
16535 Specifies the format of the reformatted output file. The @var{xxx}
16536 ^string specified with the switch^option^ may be either
16538 @item ``@option{^dos^DOS^}'' MS DOS style, lines end with CR LF characters
16539 @item ``@option{^crlf^CRLF^}''
16540 the same as @option{^crlf^CRLF^}
16541 @item ``@option{^unix^UNIX^}'' UNIX style, lines end with LF character
16542 @item ``@option{^lf^LF^}''
16543 the same as @option{^unix^UNIX^}
16546 @item ^-W^/RESULT_ENCODING=^@var{e}
16547 @cindex @option{^-W^/RESULT_ENCODING=^} (@command{gnatpp})
16548 Specify the wide character encoding method used to write the code in the
16550 @var{e} is one of the following:
16558 Upper half encoding
16560 @item ^s^SHIFT_JIS^
16570 Brackets encoding (default value)
16576 Options @option{^-pipe^/STANDARD_OUTPUT^},
16577 @option{^-o^/OUTPUT^} and
16578 @option{^-of^/FORCED_OUTPUT^} are allowed only if the call to gnatpp
16579 contains only one file to reformat.
16581 @option{^--eol^/END_OF_LINE^}
16583 @option{^-W^/RESULT_ENCODING^}
16584 cannot be used together
16585 with @option{^-pipe^/STANDARD_OUTPUT^} option.
16587 @node Other gnatpp Switches
16588 @subsection Other @code{gnatpp} Switches
16591 The additional @command{gnatpp} switches are defined in this subsection.
16594 @item ^-files @var{filename}^/FILES=@var{output_file}^
16595 @cindex @option{^-files^/FILES^} (@code{gnatpp})
16596 Take the argument source files from the specified file. This file should be an
16597 ordinary textual file containing file names separated by spaces or
16598 line breaks. You can use this switch more then once in the same call to
16599 @command{gnatpp}. You also can combine this switch with explicit list of
16602 @item ^-v^/VERBOSE^
16603 @cindex @option{^-v^/VERBOSE^} (@code{gnatpp})
16605 @command{gnatpp} generates version information and then
16606 a trace of the actions it takes to produce or obtain the ASIS tree.
16608 @item ^-w^/WARNINGS^
16609 @cindex @option{^-w^/WARNINGS^} (@code{gnatpp})
16611 @command{gnatpp} generates a warning whenever it cannot provide
16612 a required layout in the result source.
16615 @node Formatting Rules
16616 @section Formatting Rules
16619 The following subsections show how @command{gnatpp} treats ``white space'',
16620 comments, program layout, and name casing.
16621 They provide the detailed descriptions of the switches shown above.
16624 * White Space and Empty Lines::
16625 * Formatting Comments::
16626 * Construct Layout::
16630 @node White Space and Empty Lines
16631 @subsection White Space and Empty Lines
16634 @command{gnatpp} does not have an option to control space characters.
16635 It will add or remove spaces according to the style illustrated by the
16636 examples in the @cite{Ada Reference Manual}.
16638 The only format effectors
16639 (see @cite{Ada Reference Manual}, paragraph 2.1(13))
16640 that will appear in the output file are platform-specific line breaks,
16641 and also format effectors within (but not at the end of) comments.
16642 In particular, each horizontal tab character that is not inside
16643 a comment will be treated as a space and thus will appear in the
16644 output file as zero or more spaces depending on
16645 the reformatting of the line in which it appears.
16646 The only exception is a Form Feed character, which is inserted after a
16647 pragma @code{Page} when @option{-ff} is set.
16649 The output file will contain no lines with trailing ``white space'' (spaces,
16652 Empty lines in the original source are preserved
16653 only if they separate declarations or statements.
16654 In such contexts, a
16655 sequence of two or more empty lines is replaced by exactly one empty line.
16656 Note that a blank line will be removed if it separates two ``comment blocks''
16657 (a comment block is a sequence of whole-line comments).
16658 In order to preserve a visual separation between comment blocks, use an
16659 ``empty comment'' (a line comprising only hyphens) rather than an empty line.
16660 Likewise, if for some reason you wish to have a sequence of empty lines,
16661 use a sequence of empty comments instead.
16663 @node Formatting Comments
16664 @subsection Formatting Comments
16667 Comments in Ada code are of two kinds:
16670 a @emph{whole-line comment}, which appears by itself (possibly preceded by
16671 ``white space'') on a line
16674 an @emph{end-of-line comment}, which follows some other Ada lexical element
16679 The indentation of a whole-line comment is that of either
16680 the preceding or following line in
16681 the formatted source, depending on switch settings as will be described below.
16683 For an end-of-line comment, @command{gnatpp} leaves the same number of spaces
16684 between the end of the preceding Ada lexical element and the beginning
16685 of the comment as appear in the original source,
16686 unless either the comment has to be split to
16687 satisfy the line length limitation, or else the next line contains a
16688 whole line comment that is considered a continuation of this end-of-line
16689 comment (because it starts at the same position).
16691 cases, the start of the end-of-line comment is moved right to the nearest
16692 multiple of the indentation level.
16693 This may result in a ``line overflow'' (the right-shifted comment extending
16694 beyond the maximum line length), in which case the comment is split as
16697 There is a difference between @option{^-c1^/COMMENTS_LAYOUT=DEFAULT^}
16698 (GNAT-style comment line indentation)
16699 and @option{^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^}
16700 (reference-manual comment line indentation).
16701 With reference-manual style, a whole-line comment is indented as if it
16702 were a declaration or statement at the same place
16703 (i.e., according to the indentation of the preceding line(s)).
16704 With GNAT style, a whole-line comment that is immediately followed by an
16705 @b{if} or @b{case} statement alternative, a record variant, or the reserved
16706 word @b{begin}, is indented based on the construct that follows it.
16709 @smallexample @c ada
16721 Reference-manual indentation produces:
16723 @smallexample @c ada
16735 while GNAT-style indentation produces:
16737 @smallexample @c ada
16749 The @option{^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^} switch
16750 (GNAT style comment beginning) has the following
16755 For each whole-line comment that does not end with two hyphens,
16756 @command{gnatpp} inserts spaces if necessary after the starting two hyphens
16757 to ensure that there are at least two spaces between these hyphens and the
16758 first non-blank character of the comment.
16762 For an end-of-line comment, if in the original source the next line is a
16763 whole-line comment that starts at the same position
16764 as the end-of-line comment,
16765 then the whole-line comment (and all whole-line comments
16766 that follow it and that start at the same position)
16767 will start at this position in the output file.
16770 That is, if in the original source we have:
16772 @smallexample @c ada
16775 A := B + C; -- B must be in the range Low1..High1
16776 -- C must be in the range Low2..High2
16777 --B+C will be in the range Low1+Low2..High1+High2
16783 Then in the formatted source we get
16785 @smallexample @c ada
16788 A := B + C; -- B must be in the range Low1..High1
16789 -- C must be in the range Low2..High2
16790 -- B+C will be in the range Low1+Low2..High1+High2
16796 A comment that exceeds the line length limit will be split.
16798 @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} (reformat comment blocks) is set and
16799 the line belongs to a reformattable block, splitting the line generates a
16800 @command{gnatpp} warning.
16801 The @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} switch specifies that whole-line
16802 comments may be reformatted in typical
16803 word processor style (that is, moving words between lines and putting as
16804 many words in a line as possible).
16807 The @option{^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^} switch specifies, that comments
16808 that has a special format (that is, a character that is neither a letter nor digit
16809 not white space nor line break immediately following the leading @code{--} of
16810 the comment) should be without any change moved from the argument source
16811 into reformatted source. This switch allows to preserve comments that are used
16812 as a special marks in the code (e.g.@: SPARK annotation).
16814 @node Construct Layout
16815 @subsection Construct Layout
16818 In several cases the suggested layout in the Ada Reference Manual includes
16819 an extra level of indentation that many programmers prefer to avoid. The
16820 affected cases include:
16824 @item Record type declaration (RM 3.8)
16826 @item Record representation clause (RM 13.5.1)
16828 @item Loop statement in case if a loop has a statement identifier (RM 5.6)
16830 @item Block statement in case if a block has a statement identifier (RM 5.6)
16834 In compact mode (when GNAT style layout or compact layout is set),
16835 the pretty printer uses one level of indentation instead
16836 of two. This is achieved in the record definition and record representation
16837 clause cases by putting the @code{record} keyword on the same line as the
16838 start of the declaration or representation clause, and in the block and loop
16839 case by putting the block or loop header on the same line as the statement
16843 The difference between GNAT style @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^}
16844 and compact @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^}
16845 layout on the one hand, and uncompact layout
16846 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} on the other hand,
16847 can be illustrated by the following examples:
16851 @multitable @columnfractions .5 .5
16852 @item @i{GNAT style, compact layout} @tab @i{Uncompact layout}
16855 @smallexample @c ada
16862 @smallexample @c ada
16871 @smallexample @c ada
16873 a at 0 range 0 .. 31;
16874 b at 4 range 0 .. 31;
16878 @smallexample @c ada
16881 a at 0 range 0 .. 31;
16882 b at 4 range 0 .. 31;
16887 @smallexample @c ada
16895 @smallexample @c ada
16905 @smallexample @c ada
16906 Clear : for J in 1 .. 10 loop
16911 @smallexample @c ada
16913 for J in 1 .. 10 loop
16924 GNAT style, compact layout Uncompact layout
16926 type q is record type q is
16927 a : integer; record
16928 b : integer; a : integer;
16929 end record; b : integer;
16932 for q use record for q use
16933 a at 0 range 0 .. 31; record
16934 b at 4 range 0 .. 31; a at 0 range 0 .. 31;
16935 end record; b at 4 range 0 .. 31;
16938 Block : declare Block :
16939 A : Integer := 3; declare
16940 begin A : Integer := 3;
16942 end Block; Proc (A, A);
16945 Clear : for J in 1 .. 10 loop Clear :
16946 A (J) := 0; for J in 1 .. 10 loop
16947 end loop Clear; A (J) := 0;
16954 A further difference between GNAT style layout and compact layout is that
16955 GNAT style layout inserts empty lines as separation for
16956 compound statements, return statements and bodies.
16958 Note that the layout specified by
16959 @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^}
16960 for named block and loop statements overrides the layout defined by these
16961 constructs by @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^},
16962 @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^} or
16963 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} option.
16966 @subsection Name Casing
16969 @command{gnatpp} always converts the usage occurrence of a (simple) name to
16970 the same casing as the corresponding defining identifier.
16972 You control the casing for defining occurrences via the
16973 @option{^-n^/NAME_CASING^} switch.
16975 With @option{-nD} (``as declared'', which is the default),
16978 With @option{/NAME_CASING=AS_DECLARED}, which is the default,
16980 defining occurrences appear exactly as in the source file
16981 where they are declared.
16982 The other ^values for this switch^options for this qualifier^ ---
16983 @option{^-nU^UPPER_CASE^},
16984 @option{^-nL^LOWER_CASE^},
16985 @option{^-nM^MIXED_CASE^} ---
16987 ^upper, lower, or mixed case, respectively^the corresponding casing^.
16988 If @command{gnatpp} changes the casing of a defining
16989 occurrence, it analogously changes the casing of all the
16990 usage occurrences of this name.
16992 If the defining occurrence of a name is not in the source compilation unit
16993 currently being processed by @command{gnatpp}, the casing of each reference to
16994 this name is changed according to the value of the @option{^-n^/NAME_CASING^}
16995 switch (subject to the dictionary file mechanism described below).
16996 Thus @command{gnatpp} acts as though the @option{^-n^/NAME_CASING^} switch
16998 casing for the defining occurrence of the name.
17000 Some names may need to be spelled with casing conventions that are not
17001 covered by the upper-, lower-, and mixed-case transformations.
17002 You can arrange correct casing by placing such names in a
17003 @emph{dictionary file},
17004 and then supplying a @option{^-D^/DICTIONARY^} switch.
17005 The casing of names from dictionary files overrides
17006 any @option{^-n^/NAME_CASING^} switch.
17008 To handle the casing of Ada predefined names and the names from GNAT libraries,
17009 @command{gnatpp} assumes a default dictionary file.
17010 The name of each predefined entity is spelled with the same casing as is used
17011 for the entity in the @cite{Ada Reference Manual}.
17012 The name of each entity in the GNAT libraries is spelled with the same casing
17013 as is used in the declaration of that entity.
17015 The @w{@option{^-D-^/SPECIFIC_CASING^}} switch suppresses the use of the
17016 default dictionary file.
17017 Instead, the casing for predefined and GNAT-defined names will be established
17018 by the @option{^-n^/NAME_CASING^} switch or explicit dictionary files.
17019 For example, by default the names @code{Ada.Text_IO} and @code{GNAT.OS_Lib}
17020 will appear as just shown,
17021 even in the presence of a @option{^-nU^/NAME_CASING=UPPER_CASE^} switch.
17022 To ensure that even such names are rendered in uppercase,
17023 additionally supply the @w{@option{^-D-^/SPECIFIC_CASING^}} switch
17024 (or else, less conveniently, place these names in upper case in a dictionary
17027 A dictionary file is
17028 a plain text file; each line in this file can be either a blank line
17029 (containing only space characters and ASCII.HT characters), an Ada comment
17030 line, or the specification of exactly one @emph{casing schema}.
17032 A casing schema is a string that has the following syntax:
17036 @var{casing_schema} ::= @var{identifier} | *@var{simple_identifier}*
17038 @var{simple_identifier} ::= @var{letter}@{@var{letter_or_digit}@}
17043 (See @cite{Ada Reference Manual}, Section 2.3) for the definition of the
17044 @var{identifier} lexical element and the @var{letter_or_digit} category.)
17046 The casing schema string can be followed by white space and/or an Ada-style
17047 comment; any amount of white space is allowed before the string.
17049 If a dictionary file is passed as
17051 the value of a @option{-D@var{file}} switch
17054 an option to the @option{/DICTIONARY} qualifier
17057 simple name and every identifier, @command{gnatpp} checks if the dictionary
17058 defines the casing for the name or for some of its parts (the term ``subword''
17059 is used below to denote the part of a name which is delimited by ``_'' or by
17060 the beginning or end of the word and which does not contain any ``_'' inside):
17064 if the whole name is in the dictionary, @command{gnatpp} uses for this name
17065 the casing defined by the dictionary; no subwords are checked for this word
17068 for every subword @command{gnatpp} checks if the dictionary contains the
17069 corresponding string of the form @code{*@var{simple_identifier}*},
17070 and if it does, the casing of this @var{simple_identifier} is used
17074 if the whole name does not contain any ``_'' inside, and if for this name
17075 the dictionary contains two entries - one of the form @var{identifier},
17076 and another - of the form *@var{simple_identifier}*, then the first one
17077 is applied to define the casing of this name
17080 if more than one dictionary file is passed as @command{gnatpp} switches, each
17081 dictionary adds new casing exceptions and overrides all the existing casing
17082 exceptions set by the previous dictionaries
17085 when @command{gnatpp} checks if the word or subword is in the dictionary,
17086 this check is not case sensitive
17090 For example, suppose we have the following source to reformat:
17092 @smallexample @c ada
17095 name1 : integer := 1;
17096 name4_name3_name2 : integer := 2;
17097 name2_name3_name4 : Boolean;
17100 name2_name3_name4 := name4_name3_name2 > name1;
17106 And suppose we have two dictionaries:
17123 If @command{gnatpp} is called with the following switches:
17127 @command{gnatpp -nM -D dict1 -D dict2 test.adb}
17130 @command{gnatpp test.adb /NAME_CASING=MIXED_CASE /DICTIONARY=(dict1, dict2)}
17135 then we will get the following name casing in the @command{gnatpp} output:
17137 @smallexample @c ada
17140 NAME1 : Integer := 1;
17141 Name4_NAME3_Name2 : Integer := 2;
17142 Name2_NAME3_Name4 : Boolean;
17145 Name2_NAME3_Name4 := Name4_NAME3_Name2 > NAME1;
17150 @c *********************************
17151 @node The GNAT Metric Tool gnatmetric
17152 @chapter The GNAT Metric Tool @command{gnatmetric}
17154 @cindex Metric tool
17157 ^The @command{gnatmetric} tool^@command{GNAT METRIC}^ is an ASIS-based utility
17158 for computing various program metrics.
17159 It takes an Ada source file as input and generates a file containing the
17160 metrics data as output. Various switches control which
17161 metrics are computed and output.
17163 @command{gnatmetric} generates and uses the ASIS
17164 tree for the input source and thus requires the input to be syntactically and
17165 semantically legal.
17166 If this condition is not met, @command{gnatmetric} will generate
17167 an error message; no metric information for this file will be
17168 computed and reported.
17170 If the compilation unit contained in the input source depends semantically
17171 upon units in files located outside the current directory, you have to provide
17172 the source search path when invoking @command{gnatmetric}.
17173 If it depends semantically upon units that are contained
17174 in files with names that do not follow the GNAT file naming rules, you have to
17175 provide the configuration file describing the corresponding naming scheme (see
17176 the description of the @command{gnatmetric} switches below.)
17177 Alternatively, you may use a project file and invoke @command{gnatmetric}
17178 through the @command{gnat} driver.
17180 The @command{gnatmetric} command has the form
17183 $ gnatmetric @ovar{switches} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]}
17190 @var{switches} specify the metrics to compute and define the destination for
17194 Each @var{filename} is the name (including the extension) of a source
17195 file to process. ``Wildcards'' are allowed, and
17196 the file name may contain path information.
17197 If no @var{filename} is supplied, then the @var{switches} list must contain
17199 @option{-files} switch (@pxref{Other gnatmetric Switches}).
17200 Including both a @option{-files} switch and one or more
17201 @var{filename} arguments is permitted.
17204 @samp{-cargs @var{gcc_switches}} is a list of switches for
17205 @command{gcc}. They will be passed on to all compiler invocations made by
17206 @command{gnatmetric} to generate the ASIS trees. Here you can provide
17207 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
17208 and use the @option{-gnatec} switch to set the configuration file.
17212 * Switches for gnatmetric::
17215 @node Switches for gnatmetric
17216 @section Switches for @command{gnatmetric}
17219 The following subsections describe the various switches accepted by
17220 @command{gnatmetric}, organized by category.
17223 * Output Files Control::
17224 * Disable Metrics For Local Units::
17225 * Specifying a set of metrics to compute::
17226 * Other gnatmetric Switches::
17227 * Generate project-wide metrics::
17230 @node Output Files Control
17231 @subsection Output File Control
17232 @cindex Output file control in @command{gnatmetric}
17235 @command{gnatmetric} has two output formats. It can generate a
17236 textual (human-readable) form, and also XML. By default only textual
17237 output is generated.
17239 When generating the output in textual form, @command{gnatmetric} creates
17240 for each Ada source file a corresponding text file
17241 containing the computed metrics, except for the case when the set of metrics
17242 specified by gnatmetric parameters consists only of metrics that are computed
17243 for the whole set of analyzed sources, but not for each Ada source.
17244 By default, this file is placed in the same directory as where the source
17245 file is located, and its name is obtained
17246 by appending the ^@file{.metrix}^@file{$METRIX}^ suffix to the name of the
17249 All the output information generated in XML format is placed in a single
17250 file. By default this file is placed in the current directory and has the
17251 name ^@file{metrix.xml}^@file{METRIX$XML}^.
17253 Some of the computed metrics are summed over the units passed to
17254 @command{gnatmetric}; for example, the total number of lines of code.
17255 By default this information is sent to @file{stdout}, but a file
17256 can be specified with the @option{-og} switch.
17258 The following switches control the @command{gnatmetric} output:
17261 @cindex @option{^-x^/XML^} (@command{gnatmetric})
17263 Generate the XML output
17265 @cindex @option{^-xs^/XSD^} (@command{gnatmetric})
17267 Generate the XML output and the XML schema file that describes the structure
17268 of the XML metric report, this schema is assigned to the XML file. The schema
17269 file has the same name as the XML output file with @file{.xml} suffix replaced
17272 @cindex @option{^-nt^/NO_TEXT^} (@command{gnatmetric})
17273 @item ^-nt^/NO_TEXT^
17274 Do not generate the output in text form (implies @option{^-x^/XML^})
17276 @cindex @option{^-d^/DIRECTORY^} (@command{gnatmetric})
17277 @item ^-d @var{output_dir}^/DIRECTORY=@var{output_dir}^
17278 Put textual files with detailed metrics into @var{output_dir}
17280 @cindex @option{^-o^/SUFFIX_DETAILS^} (@command{gnatmetric})
17281 @item ^-o @var{file_suffix}^/SUFFIX_DETAILS=@var{file_suffix}^
17282 Use @var{file_suffix}, instead of ^@file{.metrix}^@file{$METRIX}^
17283 in the name of the output file.
17285 @cindex @option{^-og^/GLOBAL_OUTPUT^} (@command{gnatmetric})
17286 @item ^-og @var{file_name}^/GLOBAL_OUTPUT=@var{file_name}^
17287 Put global metrics into @var{file_name}
17289 @cindex @option{^-ox^/XML_OUTPUT^} (@command{gnatmetric})
17290 @item ^-ox @var{file_name}^/XML_OUTPUT=@var{file_name}^
17291 Put the XML output into @var{file_name} (also implies @option{^-x^/XML^})
17293 @cindex @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} (@command{gnatmetric})
17294 @item ^-sfn^/SHORT_SOURCE_FILE_NAME^
17295 Use ``short'' source file names in the output. (The @command{gnatmetric}
17296 output includes the name(s) of the Ada source file(s) from which the metrics
17297 are computed. By default each name includes the absolute path. The
17298 @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} switch causes @command{gnatmetric}
17299 to exclude all directory information from the file names that are output.)
17303 @node Disable Metrics For Local Units
17304 @subsection Disable Metrics For Local Units
17305 @cindex Disable Metrics For Local Units in @command{gnatmetric}
17308 @command{gnatmetric} relies on the GNAT compilation model @minus{}
17310 unit per one source file. It computes line metrics for the whole source
17311 file, and it also computes syntax
17312 and complexity metrics for the file's outermost unit.
17314 By default, @command{gnatmetric} will also compute all metrics for certain
17315 kinds of locally declared program units:
17319 subprogram (and generic subprogram) bodies;
17322 package (and generic package) specs and bodies;
17325 task object and type specifications and bodies;
17328 protected object and type specifications and bodies.
17332 These kinds of entities will be referred to as
17333 @emph{eligible local program units}, or simply @emph{eligible local units},
17334 @cindex Eligible local unit (for @command{gnatmetric})
17335 in the discussion below.
17337 Note that a subprogram declaration, generic instantiation,
17338 or renaming declaration only receives metrics
17339 computation when it appear as the outermost entity
17342 Suppression of metrics computation for eligible local units can be
17343 obtained via the following switch:
17346 @cindex @option{^-n@var{x}^/SUPPRESS^} (@command{gnatmetric})
17347 @item ^-nolocal^/SUPPRESS=LOCAL_DETAILS^
17348 Do not compute detailed metrics for eligible local program units
17352 @node Specifying a set of metrics to compute
17353 @subsection Specifying a set of metrics to compute
17356 By default all the metrics are computed and reported. The switches
17357 described in this subsection allow you to control, on an individual
17358 basis, whether metrics are computed and
17359 reported. If at least one positive metric
17360 switch is specified (that is, a switch that defines that a given
17361 metric or set of metrics is to be computed), then only
17362 explicitly specified metrics are reported.
17365 * Line Metrics Control::
17366 * Syntax Metrics Control::
17367 * Complexity Metrics Control::
17368 * Object-Oriented Metrics Control::
17371 @node Line Metrics Control
17372 @subsubsection Line Metrics Control
17373 @cindex Line metrics control in @command{gnatmetric}
17376 For any (legal) source file, and for each of its
17377 eligible local program units, @command{gnatmetric} computes the following
17382 the total number of lines;
17385 the total number of code lines (i.e., non-blank lines that are not comments)
17388 the number of comment lines
17391 the number of code lines containing end-of-line comments;
17394 the comment percentage: the ratio between the number of lines that contain
17395 comments and the number of all non-blank lines, expressed as a percentage;
17398 the number of empty lines and lines containing only space characters and/or
17399 format effectors (blank lines)
17402 the average number of code lines in subprogram bodies, task bodies, entry
17403 bodies and statement sequences in package bodies (this metric is only computed
17404 across the whole set of the analyzed units)
17409 @command{gnatmetric} sums the values of the line metrics for all the
17410 files being processed and then generates the cumulative results. The tool
17411 also computes for all the files being processed the average number of code
17414 You can use the following switches to select the specific line metrics
17415 to be computed and reported.
17418 @cindex @option{^--lines@var{x}^/LINE_COUNT_METRICS^} (@command{gnatmetric})
17421 @cindex @option{--no-lines@var{x}}
17424 @item ^--lines-all^/LINE_COUNT_METRICS=ALL^
17425 Report all the line metrics
17427 @item ^--no-lines-all^/LINE_COUNT_METRICS=NONE^
17428 Do not report any of line metrics
17430 @item ^--lines^/LINE_COUNT_METRICS=ALL_LINES^
17431 Report the number of all lines
17433 @item ^--no-lines^/LINE_COUNT_METRICS=NOALL_LINES^
17434 Do not report the number of all lines
17436 @item ^--lines-code^/LINE_COUNT_METRICS=CODE_LINES^
17437 Report the number of code lines
17439 @item ^--no-lines-code^/LINE_COUNT_METRICS=NOCODE_LINES^
17440 Do not report the number of code lines
17442 @item ^--lines-comment^/LINE_COUNT_METRICS=COMMENT_LINES^
17443 Report the number of comment lines
17445 @item ^--no-lines-comment^/LINE_COUNT_METRICS=NOCOMMENT_LINES^
17446 Do not report the number of comment lines
17448 @item ^--lines-eol-comment^/LINE_COUNT_METRICS=CODE_COMMENT_LINES^
17449 Report the number of code lines containing
17450 end-of-line comments
17452 @item ^--no-lines-eol-comment^/LINE_COUNT_METRICS=NOCODE_COMMENT_LINES^
17453 Do not report the number of code lines containing
17454 end-of-line comments
17456 @item ^--lines-ratio^/LINE_COUNT_METRICS=COMMENT_PERCENTAGE^
17457 Report the comment percentage in the program text
17459 @item ^--no-lines-ratio^/LINE_COUNT_METRICS=NOCOMMENT_PERCENTAGE^
17460 Do not report the comment percentage in the program text
17462 @item ^--lines-blank^/LINE_COUNT_METRICS=BLANK_LINES^
17463 Report the number of blank lines
17465 @item ^--no-lines-blank^/LINE_COUNT_METRICS=NOBLANK_LINES^
17466 Do not report the number of blank lines
17468 @item ^--lines-average^/LINE_COUNT_METRICS=AVERAGE_BODY_LINES^
17469 Report the average number of code lines in subprogram bodies, task bodies,
17470 entry bodies and statement sequences in package bodies. The metric is computed
17471 and reported for the whole set of processed Ada sources only.
17473 @item ^--no-lines-average^/LINE_COUNT_METRICS=NOAVERAGE_BODY_LINES^
17474 Do not report the average number of code lines in subprogram bodies,
17475 task bodies, entry bodies and statement sequences in package bodies.
17479 @node Syntax Metrics Control
17480 @subsubsection Syntax Metrics Control
17481 @cindex Syntax metrics control in @command{gnatmetric}
17484 @command{gnatmetric} computes various syntactic metrics for the
17485 outermost unit and for each eligible local unit:
17488 @item LSLOC (``Logical Source Lines Of Code'')
17489 The total number of declarations and the total number of statements
17491 @item Maximal static nesting level of inner program units
17493 @cite{Ada Reference Manual}, 10.1(1), ``A program unit is either a
17494 package, a task unit, a protected unit, a
17495 protected entry, a generic unit, or an explicitly declared subprogram other
17496 than an enumeration literal.''
17498 @item Maximal nesting level of composite syntactic constructs
17499 This corresponds to the notion of the
17500 maximum nesting level in the GNAT built-in style checks
17501 (@pxref{Style Checking})
17505 For the outermost unit in the file, @command{gnatmetric} additionally computes
17506 the following metrics:
17509 @item Public subprograms
17510 This metric is computed for package specs. It is the
17511 number of subprograms and generic subprograms declared in the visible
17512 part (including the visible part of nested packages, protected objects, and
17515 @item All subprograms
17516 This metric is computed for bodies and subunits. The
17517 metric is equal to a total number of subprogram bodies in the compilation
17519 Neither generic instantiations nor renamings-as-a-body nor body stubs
17520 are counted. Any subprogram body is counted, independently of its nesting
17521 level and enclosing constructs. Generic bodies and bodies of protected
17522 subprograms are counted in the same way as ``usual'' subprogram bodies.
17525 This metric is computed for package specs and
17526 generic package declarations. It is the total number of types
17527 that can be referenced from outside this compilation unit, plus the
17528 number of types from all the visible parts of all the visible generic
17529 packages. Generic formal types are not counted. Only types, not subtypes,
17533 Along with the total number of public types, the following
17534 types are counted and reported separately:
17541 Root tagged types (abstract, non-abstract, private, non-private). Type
17542 extensions are @emph{not} counted
17545 Private types (including private extensions)
17556 This metric is computed for any compilation unit. It is equal to the total
17557 number of the declarations of different types given in the compilation unit.
17558 The private and the corresponding full type declaration are counted as one
17559 type declaration. Incomplete type declarations and generic formal types
17561 No distinction is made among different kinds of types (abstract,
17562 private etc.); the total number of types is computed and reported.
17567 By default, all the syntax metrics are computed and reported. You can use the
17568 following switches to select specific syntax metrics.
17572 @cindex @option{^--syntax@var{x}^/SYNTAX_METRICS^} (@command{gnatmetric})
17575 @cindex @option{--no-syntax@var{x}} (@command{gnatmetric})
17578 @item ^--syntax-all^/SYNTAX_METRICS=ALL^
17579 Report all the syntax metrics
17581 @item ^--no-syntax-all^/SYNTAX_METRICS=NONE^
17582 Do not report any of syntax metrics
17584 @item ^--declarations^/SYNTAX_METRICS=DECLARATIONS^
17585 Report the total number of declarations
17587 @item ^--no-declarations^/SYNTAX_METRICS=NODECLARATIONS^
17588 Do not report the total number of declarations
17590 @item ^--statements^/SYNTAX_METRICS=STATEMENTS^
17591 Report the total number of statements
17593 @item ^--no-statements^/SYNTAX_METRICS=NOSTATEMENTS^
17594 Do not report the total number of statements
17596 @item ^--public-subprograms^/SYNTAX_METRICS=PUBLIC_SUBPROGRAMS^
17597 Report the number of public subprograms in a compilation unit
17599 @item ^--no-public-subprograms^/SYNTAX_METRICS=NOPUBLIC_SUBPROGRAMS^
17600 Do not report the number of public subprograms in a compilation unit
17602 @item ^--all-subprograms^/SYNTAX_METRICS=ALL_SUBPROGRAMS^
17603 Report the number of all the subprograms in a compilation unit
17605 @item ^--no-all-subprograms^/SYNTAX_METRICS=NOALL_SUBPROGRAMS^
17606 Do not report the number of all the subprograms in a compilation unit
17608 @item ^--public-types^/SYNTAX_METRICS=PUBLIC_TYPES^
17609 Report the number of public types in a compilation unit
17611 @item ^--no-public-types^/SYNTAX_METRICS=NOPUBLIC_TYPES^
17612 Do not report the number of public types in a compilation unit
17614 @item ^--all-types^/SYNTAX_METRICS=ALL_TYPES^
17615 Report the number of all the types in a compilation unit
17617 @item ^--no-all-types^/SYNTAX_METRICS=NOALL_TYPES^
17618 Do not report the number of all the types in a compilation unit
17620 @item ^--unit-nesting^/SYNTAX_METRICS=UNIT_NESTING^
17621 Report the maximal program unit nesting level
17623 @item ^--no-unit-nesting^/SYNTAX_METRICS=UNIT_NESTING_OFF^
17624 Do not report the maximal program unit nesting level
17626 @item ^--construct-nesting^/SYNTAX_METRICS=CONSTRUCT_NESTING^
17627 Report the maximal construct nesting level
17629 @item ^--no-construct-nesting^/SYNTAX_METRICS=NOCONSTRUCT_NESTING^
17630 Do not report the maximal construct nesting level
17634 @node Complexity Metrics Control
17635 @subsubsection Complexity Metrics Control
17636 @cindex Complexity metrics control in @command{gnatmetric}
17639 For a program unit that is an executable body (a subprogram body (including
17640 generic bodies), task body, entry body or a package body containing
17641 its own statement sequence) @command{gnatmetric} computes the following
17642 complexity metrics:
17646 McCabe cyclomatic complexity;
17649 McCabe essential complexity;
17652 maximal loop nesting level
17657 The McCabe complexity metrics are defined
17658 in @url{http://www.mccabe.com/pdf/nist235r.pdf}
17660 According to McCabe, both control statements and short-circuit control forms
17661 should be taken into account when computing cyclomatic complexity. For each
17662 body, we compute three metric values:
17666 the complexity introduced by control
17667 statements only, without taking into account short-circuit forms,
17670 the complexity introduced by short-circuit control forms only, and
17674 cyclomatic complexity, which is the sum of these two values.
17678 When computing cyclomatic and essential complexity, @command{gnatmetric} skips
17679 the code in the exception handlers and in all the nested program units.
17681 By default, all the complexity metrics are computed and reported.
17682 For more fine-grained control you can use
17683 the following switches:
17686 @cindex @option{^-complexity@var{x}^/COMPLEXITY_METRICS^} (@command{gnatmetric})
17689 @cindex @option{--no-complexity@var{x}}
17692 @item ^--complexity-all^/COMPLEXITY_METRICS=ALL^
17693 Report all the complexity metrics
17695 @item ^--no-complexity-all^/COMPLEXITY_METRICS=NONE^
17696 Do not report any of complexity metrics
17698 @item ^--complexity-cyclomatic^/COMPLEXITY_METRICS=CYCLOMATIC^
17699 Report the McCabe Cyclomatic Complexity
17701 @item ^--no-complexity-cyclomatic^/COMPLEXITY_METRICS=NOCYCLOMATIC^
17702 Do not report the McCabe Cyclomatic Complexity
17704 @item ^--complexity-essential^/COMPLEXITY_METRICS=ESSENTIAL^
17705 Report the Essential Complexity
17707 @item ^--no-complexity-essential^/COMPLEXITY_METRICS=NOESSENTIAL^
17708 Do not report the Essential Complexity
17710 @item ^--loop-nesting^/COMPLEXITY_METRICS=LOOP_NESTING_ON^
17711 Report maximal loop nesting level
17713 @item ^--no-loop-nesting^/COMPLEXITY_METRICS=NOLOOP_NESTING^
17714 Do not report maximal loop nesting level
17716 @item ^--complexity-average^/COMPLEXITY_METRICS=AVERAGE_COMPLEXITY^
17717 Report the average McCabe Cyclomatic Complexity for all the subprogram bodies,
17718 task bodies, entry bodies and statement sequences in package bodies.
17719 The metric is computed and reported for whole set of processed Ada sources
17722 @item ^--no-complexity-average^/COMPLEXITY_METRICS=NOAVERAGE_COMPLEXITY^
17723 Do not report the average McCabe Cyclomatic Complexity for all the subprogram
17724 bodies, task bodies, entry bodies and statement sequences in package bodies
17726 @cindex @option{^-ne^/NO_EXITS_AS_GOTOS^} (@command{gnatmetric})
17727 @item ^-ne^/NO_EXITS_AS_GOTOS^
17728 Do not consider @code{exit} statements as @code{goto}s when
17729 computing Essential Complexity
17731 @item ^--extra-exit-points^/EXTRA_EXIT_POINTS^
17732 Report the extra exit points for subprogram bodies. As an exit point, this
17733 metric counts @code{return} statements and raise statements in case when the
17734 raised exception is not handled in the same body. In case of a function this
17735 metric subtracts 1 from the number of exit points, because a function body
17736 must contain at least one @code{return} statement.
17738 @item ^--no-extra-exit-points^/NOEXTRA_EXIT_POINTS^
17739 Do not report the extra exit points for subprogram bodies
17743 @node Object-Oriented Metrics Control
17744 @subsubsection Object-Oriented Metrics Control
17745 @cindex Object-Oriented metrics control in @command{gnatmetric}
17748 @cindex Coupling metrics (in in @command{gnatmetric})
17749 Coupling metrics are object-oriented metrics that measure the
17750 dependencies between a given class (or a group of classes) and the
17751 ``external world'' (that is, the other classes in the program). In this
17752 subsection the term ``class'' is used in its
17753 traditional object-oriented programming sense
17754 (an instantiable module that contains data and/or method members).
17755 A @emph{category} (of classes)
17756 is a group of closely related classes that are reused and/or
17759 A class @code{K}'s @emph{efferent coupling} is the number of classes
17760 that @code{K} depends upon.
17761 A category's efferent coupling is the number of classes outside the
17762 category that the classes inside the category depend upon.
17764 A class @code{K}'s @emph{afferent coupling} is the number of classes
17765 that depend upon @code{K}.
17766 A category's afferent coupling is the number of classes outside the
17767 category that depend on classes belonging to the category.
17769 Ada's implementation of the object-oriented paradigm does not use the
17770 traditional class notion, so the definition of the coupling
17771 metrics for Ada maps the class and class category notions
17772 onto Ada constructs.
17774 For the coupling metrics, several kinds of modules -- a library package,
17775 a library generic package, and a library generic package instantiation --
17776 that define a tagged type or an interface type are
17777 considered to be a class. A category consists of a library package (or
17778 a library generic package) that defines a tagged or an interface type,
17779 together with all its descendant (generic) packages that define tagged
17780 or interface types. For any package counted as a class,
17781 its body and subunits (if any) are considered
17782 together with its spec when counting the dependencies, and coupling
17783 metrics are reported for spec units only. For dependencies
17784 between classes, the Ada semantic dependencies are considered.
17785 For coupling metrics, only dependencies on units that are considered as
17786 classes, are considered.
17788 When computing coupling metrics, @command{gnatmetric} counts only
17789 dependencies between units that are arguments of the gnatmetric call.
17790 Coupling metrics are program-wide (or project-wide) metrics, so to
17791 get a valid result, you should call @command{gnatmetric} for
17792 the whole set of sources that make up your program. It can be done
17793 by calling @command{gnatmetric} from the GNAT driver with @option{-U}
17794 option (see See @ref{The GNAT Driver and Project Files} for details.
17796 By default, all the coupling metrics are disabled. You can use the following
17797 switches to specify the coupling metrics to be computed and reported:
17802 @cindex @option{--package@var{x}} (@command{gnatmetric})
17803 @cindex @option{--no-package@var{x}} (@command{gnatmetric})
17804 @cindex @option{--category@var{x}} (@command{gnatmetric})
17805 @cindex @option{--no-category@var{x}} (@command{gnatmetric})
17809 @cindex @option{/COUPLING_METRICS} (@command{gnatmetric})
17812 @item ^--coupling-all^/COUPLING_METRICS=ALL^
17813 Report all the coupling metrics
17815 @item ^--no-coupling-all^/COUPLING_METRICS=NONE^
17816 Do not report any of metrics
17818 @item ^--package-efferent-coupling^/COUPLING_METRICS=PACKAGE_EFFERENT^
17819 Report package efferent coupling
17821 @item ^--no-package-efferent-coupling^/COUPLING_METRICS=NOPACKAGE_EFFERENT^
17822 Do not report package efferent coupling
17824 @item ^--package-afferent-coupling^/COUPLING_METRICS=PACKAGE_AFFERENT^
17825 Report package afferent coupling
17827 @item ^--no-package-afferent-coupling^/COUPLING_METRICS=NOPACKAGE_AFFERENT^
17828 Do not report package afferent coupling
17830 @item ^--category-efferent-coupling^/COUPLING_METRICS=CATEGORY_EFFERENT^
17831 Report category efferent coupling
17833 @item ^--no-category-efferent-coupling^/COUPLING_METRICS=NOCATEGORY_EFFERENT^
17834 Do not report category efferent coupling
17836 @item ^--category-afferent-coupling^/COUPLING_METRICS=CATEGORY_AFFERENT^
17837 Report category afferent coupling
17839 @item ^--no-category-afferent-coupling^/COUPLING_METRICS=NOCATEGORY_AFFERENT^
17840 Do not report category afferent coupling
17844 @node Other gnatmetric Switches
17845 @subsection Other @code{gnatmetric} Switches
17848 Additional @command{gnatmetric} switches are as follows:
17851 @item ^-files @var{filename}^/FILES=@var{filename}^
17852 @cindex @option{^-files^/FILES^} (@code{gnatmetric})
17853 Take the argument source files from the specified file. This file should be an
17854 ordinary text file containing file names separated by spaces or
17855 line breaks. You can use this switch more then once in the same call to
17856 @command{gnatmetric}. You also can combine this switch with
17857 an explicit list of files.
17859 @item ^-v^/VERBOSE^
17860 @cindex @option{^-v^/VERBOSE^} (@code{gnatmetric})
17862 @command{gnatmetric} generates version information and then
17863 a trace of sources being processed.
17865 @item ^-dv^/DEBUG_OUTPUT^
17866 @cindex @option{^-dv^/DEBUG_OUTPUT^} (@code{gnatmetric})
17868 @command{gnatmetric} generates various messages useful to understand what
17869 happens during the metrics computation
17872 @cindex @option{^-q^/QUIET^} (@code{gnatmetric})
17876 @node Generate project-wide metrics
17877 @subsection Generate project-wide metrics
17879 In order to compute metrics on all units of a given project, you can use
17880 the @command{gnat} driver along with the @option{-P} option:
17886 If the project @code{proj} depends upon other projects, you can compute
17887 the metrics on the project closure using the @option{-U} option:
17889 gnat metric -Pproj -U
17893 Finally, if not all the units are relevant to a particular main
17894 program in the project closure, you can generate metrics for the set
17895 of units needed to create a given main program (unit closure) using
17896 the @option{-U} option followed by the name of the main unit:
17898 gnat metric -Pproj -U main
17902 @c ***********************************
17903 @node File Name Krunching Using gnatkr
17904 @chapter File Name Krunching Using @code{gnatkr}
17908 This chapter discusses the method used by the compiler to shorten
17909 the default file names chosen for Ada units so that they do not
17910 exceed the maximum length permitted. It also describes the
17911 @code{gnatkr} utility that can be used to determine the result of
17912 applying this shortening.
17916 * Krunching Method::
17917 * Examples of gnatkr Usage::
17921 @section About @code{gnatkr}
17924 The default file naming rule in GNAT
17925 is that the file name must be derived from
17926 the unit name. The exact default rule is as follows:
17929 Take the unit name and replace all dots by hyphens.
17931 If such a replacement occurs in the
17932 second character position of a name, and the first character is
17933 ^@samp{a}, @samp{g}, @samp{s}, or @samp{i}, ^@samp{A}, @samp{G}, @samp{S}, or @samp{I},^
17934 then replace the dot by the character
17935 ^@samp{~} (tilde)^@samp{$} (dollar sign)^
17936 instead of a minus.
17938 The reason for this exception is to avoid clashes
17939 with the standard names for children of System, Ada, Interfaces,
17940 and GNAT, which use the prefixes
17941 ^@samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},^@samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},^
17944 The @option{^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{nn}}
17945 switch of the compiler activates a ``krunching''
17946 circuit that limits file names to nn characters (where nn is a decimal
17947 integer). For example, using OpenVMS,
17948 where the maximum file name length is
17949 39, the value of nn is usually set to 39, but if you want to generate
17950 a set of files that would be usable if ported to a system with some
17951 different maximum file length, then a different value can be specified.
17952 The default value of 39 for OpenVMS need not be specified.
17954 The @code{gnatkr} utility can be used to determine the krunched name for
17955 a given file, when krunched to a specified maximum length.
17958 @section Using @code{gnatkr}
17961 The @code{gnatkr} command has the form
17965 $ gnatkr @var{name} @ovar{length}
17971 $ gnatkr @var{name} /COUNT=nn
17976 @var{name} is the uncrunched file name, derived from the name of the unit
17977 in the standard manner described in the previous section (i.e., in particular
17978 all dots are replaced by hyphens). The file name may or may not have an
17979 extension (defined as a suffix of the form period followed by arbitrary
17980 characters other than period). If an extension is present then it will
17981 be preserved in the output. For example, when krunching @file{hellofile.ads}
17982 to eight characters, the result will be hellofil.ads.
17984 Note: for compatibility with previous versions of @code{gnatkr} dots may
17985 appear in the name instead of hyphens, but the last dot will always be
17986 taken as the start of an extension. So if @code{gnatkr} is given an argument
17987 such as @file{Hello.World.adb} it will be treated exactly as if the first
17988 period had been a hyphen, and for example krunching to eight characters
17989 gives the result @file{hellworl.adb}.
17991 Note that the result is always all lower case (except on OpenVMS where it is
17992 all upper case). Characters of the other case are folded as required.
17994 @var{length} represents the length of the krunched name. The default
17995 when no argument is given is ^8^39^ characters. A length of zero stands for
17996 unlimited, in other words do not chop except for system files where the
17997 implied crunching length is always eight characters.
18000 The output is the krunched name. The output has an extension only if the
18001 original argument was a file name with an extension.
18003 @node Krunching Method
18004 @section Krunching Method
18007 The initial file name is determined by the name of the unit that the file
18008 contains. The name is formed by taking the full expanded name of the
18009 unit and replacing the separating dots with hyphens and
18010 using ^lowercase^uppercase^
18011 for all letters, except that a hyphen in the second character position is
18012 replaced by a ^tilde^dollar sign^ if the first character is
18013 ^@samp{a}, @samp{i}, @samp{g}, or @samp{s}^@samp{A}, @samp{I}, @samp{G}, or @samp{S}^.
18014 The extension is @code{.ads} for a
18015 spec and @code{.adb} for a body.
18016 Krunching does not affect the extension, but the file name is shortened to
18017 the specified length by following these rules:
18021 The name is divided into segments separated by hyphens, tildes or
18022 underscores and all hyphens, tildes, and underscores are
18023 eliminated. If this leaves the name short enough, we are done.
18026 If the name is too long, the longest segment is located (left-most
18027 if there are two of equal length), and shortened by dropping
18028 its last character. This is repeated until the name is short enough.
18030 As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb}
18031 to fit the name into 8 characters as required by some operating systems.
18034 our-strings-wide_fixed 22
18035 our strings wide fixed 19
18036 our string wide fixed 18
18037 our strin wide fixed 17
18038 our stri wide fixed 16
18039 our stri wide fixe 15
18040 our str wide fixe 14
18041 our str wid fixe 13
18047 Final file name: oustwifi.adb
18051 The file names for all predefined units are always krunched to eight
18052 characters. The krunching of these predefined units uses the following
18053 special prefix replacements:
18057 replaced by @file{^a^A^-}
18060 replaced by @file{^g^G^-}
18063 replaced by @file{^i^I^-}
18066 replaced by @file{^s^S^-}
18069 These system files have a hyphen in the second character position. That
18070 is why normal user files replace such a character with a
18071 ^tilde^dollar sign^, to
18072 avoid confusion with system file names.
18074 As an example of this special rule, consider
18075 @*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows:
18078 ada-strings-wide_fixed 22
18079 a- strings wide fixed 18
18080 a- string wide fixed 17
18081 a- strin wide fixed 16
18082 a- stri wide fixed 15
18083 a- stri wide fixe 14
18084 a- str wide fixe 13
18090 Final file name: a-stwifi.adb
18094 Of course no file shortening algorithm can guarantee uniqueness over all
18095 possible unit names, and if file name krunching is used then it is your
18096 responsibility to ensure that no name clashes occur. The utility
18097 program @code{gnatkr} is supplied for conveniently determining the
18098 krunched name of a file.
18100 @node Examples of gnatkr Usage
18101 @section Examples of @code{gnatkr} Usage
18108 $ gnatkr very_long_unit_name.ads --> velounna.ads
18109 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
18110 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
18111 $ gnatkr grandparent-parent-child --> grparchi
18113 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
18114 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
18117 @node Preprocessing Using gnatprep
18118 @chapter Preprocessing Using @code{gnatprep}
18122 This chapter discusses how to use GNAT's @code{gnatprep} utility for simple
18124 Although designed for use with GNAT, @code{gnatprep} does not depend on any
18125 special GNAT features.
18126 For further discussion of conditional compilation in general, see
18127 @ref{Conditional Compilation}.
18130 * Preprocessing Symbols::
18132 * Switches for gnatprep::
18133 * Form of Definitions File::
18134 * Form of Input Text for gnatprep::
18137 @node Preprocessing Symbols
18138 @section Preprocessing Symbols
18141 Preprocessing symbols are defined in definition files and referred to in
18142 sources to be preprocessed. A Preprocessing symbol is an identifier, following
18143 normal Ada (case-insensitive) rules for its syntax, with the restriction that
18144 all characters need to be in the ASCII set (no accented letters).
18146 @node Using gnatprep
18147 @section Using @code{gnatprep}
18150 To call @code{gnatprep} use
18153 $ gnatprep @ovar{switches} @var{infile} @var{outfile} @ovar{deffile}
18160 is an optional sequence of switches as described in the next section.
18163 is the full name of the input file, which is an Ada source
18164 file containing preprocessor directives.
18167 is the full name of the output file, which is an Ada source
18168 in standard Ada form. When used with GNAT, this file name will
18169 normally have an ads or adb suffix.
18172 is the full name of a text file containing definitions of
18173 preprocessing symbols to be referenced by the preprocessor. This argument is
18174 optional, and can be replaced by the use of the @option{-D} switch.
18178 @node Switches for gnatprep
18179 @section Switches for @code{gnatprep}
18184 @item ^-b^/BLANK_LINES^
18185 @cindex @option{^-b^/BLANK_LINES^} (@command{gnatprep})
18186 Causes both preprocessor lines and the lines deleted by
18187 preprocessing to be replaced by blank lines in the output source file,
18188 preserving line numbers in the output file.
18190 @item ^-c^/COMMENTS^
18191 @cindex @option{^-c^/COMMENTS^} (@command{gnatprep})
18192 Causes both preprocessor lines and the lines deleted
18193 by preprocessing to be retained in the output source as comments marked
18194 with the special string @code{"--! "}. This option will result in line numbers
18195 being preserved in the output file.
18197 @item ^-C^/REPLACE_IN_COMMENTS^
18198 @cindex @option{^-C^/REPLACE_IN_COMMENTS^} (@command{gnatprep})
18199 Causes comments to be scanned. Normally comments are ignored by gnatprep.
18200 If this option is specified, then comments are scanned and any $symbol
18201 substitutions performed as in program text. This is particularly useful
18202 when structured comments are used (e.g., when writing programs in the
18203 SPARK dialect of Ada). Note that this switch is not available when
18204 doing integrated preprocessing (it would be useless in this context
18205 since comments are ignored by the compiler in any case).
18207 @item ^-Dsymbol=value^/ASSOCIATE="symbol=value"^
18208 @cindex @option{^-D^/ASSOCIATE^} (@command{gnatprep})
18209 Defines a new preprocessing symbol, associated with value. If no value is given
18210 on the command line, then symbol is considered to be @code{True}. This switch
18211 can be used in place of a definition file.
18215 @cindex @option{/REMOVE} (@command{gnatprep})
18216 This is the default setting which causes lines deleted by preprocessing
18217 to be entirely removed from the output file.
18220 @item ^-r^/REFERENCE^
18221 @cindex @option{^-r^/REFERENCE^} (@command{gnatprep})
18222 Causes a @code{Source_Reference} pragma to be generated that
18223 references the original input file, so that error messages will use
18224 the file name of this original file. The use of this switch implies
18225 that preprocessor lines are not to be removed from the file, so its
18226 use will force @option{^-b^/BLANK_LINES^} mode if
18227 @option{^-c^/COMMENTS^}
18228 has not been specified explicitly.
18230 Note that if the file to be preprocessed contains multiple units, then
18231 it will be necessary to @code{gnatchop} the output file from
18232 @code{gnatprep}. If a @code{Source_Reference} pragma is present
18233 in the preprocessed file, it will be respected by
18234 @code{gnatchop ^-r^/REFERENCE^}
18235 so that the final chopped files will correctly refer to the original
18236 input source file for @code{gnatprep}.
18238 @item ^-s^/SYMBOLS^
18239 @cindex @option{^-s^/SYMBOLS^} (@command{gnatprep})
18240 Causes a sorted list of symbol names and values to be
18241 listed on the standard output file.
18243 @item ^-u^/UNDEFINED^
18244 @cindex @option{^-u^/UNDEFINED^} (@command{gnatprep})
18245 Causes undefined symbols to be treated as having the value FALSE in the context
18246 of a preprocessor test. In the absence of this option, an undefined symbol in
18247 a @code{#if} or @code{#elsif} test will be treated as an error.
18253 Note: if neither @option{-b} nor @option{-c} is present,
18254 then preprocessor lines and
18255 deleted lines are completely removed from the output, unless -r is
18256 specified, in which case -b is assumed.
18259 @node Form of Definitions File
18260 @section Form of Definitions File
18263 The definitions file contains lines of the form
18270 where symbol is a preprocessing symbol, and value is one of the following:
18274 Empty, corresponding to a null substitution
18276 A string literal using normal Ada syntax
18278 Any sequence of characters from the set
18279 (letters, digits, period, underline).
18283 Comment lines may also appear in the definitions file, starting with
18284 the usual @code{--},
18285 and comments may be added to the definitions lines.
18287 @node Form of Input Text for gnatprep
18288 @section Form of Input Text for @code{gnatprep}
18291 The input text may contain preprocessor conditional inclusion lines,
18292 as well as general symbol substitution sequences.
18294 The preprocessor conditional inclusion commands have the form
18299 #if @i{expression} @r{[}then@r{]}
18301 #elsif @i{expression} @r{[}then@r{]}
18303 #elsif @i{expression} @r{[}then@r{]}
18314 In this example, @i{expression} is defined by the following grammar:
18316 @i{expression} ::= <symbol>
18317 @i{expression} ::= <symbol> = "<value>"
18318 @i{expression} ::= <symbol> = <symbol>
18319 @i{expression} ::= <symbol> 'Defined
18320 @i{expression} ::= not @i{expression}
18321 @i{expression} ::= @i{expression} and @i{expression}
18322 @i{expression} ::= @i{expression} or @i{expression}
18323 @i{expression} ::= @i{expression} and then @i{expression}
18324 @i{expression} ::= @i{expression} or else @i{expression}
18325 @i{expression} ::= ( @i{expression} )
18328 The following restriction exists: it is not allowed to have "and" or "or"
18329 following "not" in the same expression without parentheses. For example, this
18336 This should be one of the following:
18344 For the first test (@i{expression} ::= <symbol>) the symbol must have
18345 either the value true or false, that is to say the right-hand of the
18346 symbol definition must be one of the (case-insensitive) literals
18347 @code{True} or @code{False}. If the value is true, then the
18348 corresponding lines are included, and if the value is false, they are
18351 The test (@i{expression} ::= <symbol> @code{'Defined}) is true only if
18352 the symbol has been defined in the definition file or by a @option{-D}
18353 switch on the command line. Otherwise, the test is false.
18355 The equality tests are case insensitive, as are all the preprocessor lines.
18357 If the symbol referenced is not defined in the symbol definitions file,
18358 then the effect depends on whether or not switch @option{-u}
18359 is specified. If so, then the symbol is treated as if it had the value
18360 false and the test fails. If this switch is not specified, then
18361 it is an error to reference an undefined symbol. It is also an error to
18362 reference a symbol that is defined with a value other than @code{True}
18365 The use of the @code{not} operator inverts the sense of this logical test.
18366 The @code{not} operator cannot be combined with the @code{or} or @code{and}
18367 operators, without parentheses. For example, "if not X or Y then" is not
18368 allowed, but "if (not X) or Y then" and "if not (X or Y) then" are.
18370 The @code{then} keyword is optional as shown
18372 The @code{#} must be the first non-blank character on a line, but
18373 otherwise the format is free form. Spaces or tabs may appear between
18374 the @code{#} and the keyword. The keywords and the symbols are case
18375 insensitive as in normal Ada code. Comments may be used on a
18376 preprocessor line, but other than that, no other tokens may appear on a
18377 preprocessor line. Any number of @code{elsif} clauses can be present,
18378 including none at all. The @code{else} is optional, as in Ada.
18380 The @code{#} marking the start of a preprocessor line must be the first
18381 non-blank character on the line, i.e., it must be preceded only by
18382 spaces or horizontal tabs.
18384 Symbol substitution outside of preprocessor lines is obtained by using
18392 anywhere within a source line, except in a comment or within a
18393 string literal. The identifier
18394 following the @code{$} must match one of the symbols defined in the symbol
18395 definition file, and the result is to substitute the value of the
18396 symbol in place of @code{$symbol} in the output file.
18398 Note that although the substitution of strings within a string literal
18399 is not possible, it is possible to have a symbol whose defined value is
18400 a string literal. So instead of setting XYZ to @code{hello} and writing:
18403 Header : String := "$XYZ";
18407 you should set XYZ to @code{"hello"} and write:
18410 Header : String := $XYZ;
18414 and then the substitution will occur as desired.
18417 @node The GNAT Run-Time Library Builder gnatlbr
18418 @chapter The GNAT Run-Time Library Builder @code{gnatlbr}
18420 @cindex Library builder
18423 @code{gnatlbr} is a tool for rebuilding the GNAT run time with user
18424 supplied configuration pragmas.
18427 * Running gnatlbr::
18428 * Switches for gnatlbr::
18429 * Examples of gnatlbr Usage::
18432 @node Running gnatlbr
18433 @section Running @code{gnatlbr}
18436 The @code{gnatlbr} command has the form
18439 $ GNAT LIBRARY /@r{[}CREATE@r{|}SET@r{|}DELETE@r{]}=directory @r{[}/CONFIG=file@r{]}
18442 @node Switches for gnatlbr
18443 @section Switches for @code{gnatlbr}
18446 @code{gnatlbr} recognizes the following switches:
18450 @item /CREATE=directory
18451 @cindex @code{/CREATE} (@code{gnatlbr})
18452 Create the new run-time library in the specified directory.
18454 @item /SET=directory
18455 @cindex @code{/SET} (@code{gnatlbr})
18456 Make the library in the specified directory the current run-time library.
18458 @item /DELETE=directory
18459 @cindex @code{/DELETE} (@code{gnatlbr})
18460 Delete the run-time library in the specified directory.
18463 @cindex @code{/CONFIG} (@code{gnatlbr})
18464 With /CREATE: Use the configuration pragmas in the specified file when
18465 building the library.
18467 With /SET: Use the configuration pragmas in the specified file when
18472 @node Examples of gnatlbr Usage
18473 @section Example of @code{gnatlbr} Usage
18476 Contents of VAXFLOAT.ADC:
18477 pragma Float_Representation (VAX_Float);
18479 $ GNAT LIBRARY /CREATE=[.VAXFLOAT] /CONFIG=VAXFLOAT.ADC
18481 GNAT LIBRARY rebuilds the run-time library in directory [.VAXFLOAT]
18486 @node The GNAT Library Browser gnatls
18487 @chapter The GNAT Library Browser @code{gnatls}
18489 @cindex Library browser
18492 @code{gnatls} is a tool that outputs information about compiled
18493 units. It gives the relationship between objects, unit names and source
18494 files. It can also be used to check the source dependencies of a unit
18495 as well as various characteristics.
18497 Note: to invoke @code{gnatls} with a project file, use the @code{gnat}
18498 driver (see @ref{The GNAT Driver and Project Files}).
18502 * Switches for gnatls::
18503 * Examples of gnatls Usage::
18506 @node Running gnatls
18507 @section Running @code{gnatls}
18510 The @code{gnatls} command has the form
18513 $ gnatls switches @var{object_or_ali_file}
18517 The main argument is the list of object or @file{ali} files
18518 (@pxref{The Ada Library Information Files})
18519 for which information is requested.
18521 In normal mode, without additional option, @code{gnatls} produces a
18522 four-column listing. Each line represents information for a specific
18523 object. The first column gives the full path of the object, the second
18524 column gives the name of the principal unit in this object, the third
18525 column gives the status of the source and the fourth column gives the
18526 full path of the source representing this unit.
18527 Here is a simple example of use:
18531 ^./^[]^demo1.o demo1 DIF demo1.adb
18532 ^./^[]^demo2.o demo2 OK demo2.adb
18533 ^./^[]^hello.o h1 OK hello.adb
18534 ^./^[]^instr-child.o instr.child MOK instr-child.adb
18535 ^./^[]^instr.o instr OK instr.adb
18536 ^./^[]^tef.o tef DIF tef.adb
18537 ^./^[]^text_io_example.o text_io_example OK text_io_example.adb
18538 ^./^[]^tgef.o tgef DIF tgef.adb
18542 The first line can be interpreted as follows: the main unit which is
18544 object file @file{demo1.o} is demo1, whose main source is in
18545 @file{demo1.adb}. Furthermore, the version of the source used for the
18546 compilation of demo1 has been modified (DIF). Each source file has a status
18547 qualifier which can be:
18550 @item OK (unchanged)
18551 The version of the source file used for the compilation of the
18552 specified unit corresponds exactly to the actual source file.
18554 @item MOK (slightly modified)
18555 The version of the source file used for the compilation of the
18556 specified unit differs from the actual source file but not enough to
18557 require recompilation. If you use gnatmake with the qualifier
18558 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}, a file marked
18559 MOK will not be recompiled.
18561 @item DIF (modified)
18562 No version of the source found on the path corresponds to the source
18563 used to build this object.
18565 @item ??? (file not found)
18566 No source file was found for this unit.
18568 @item HID (hidden, unchanged version not first on PATH)
18569 The version of the source that corresponds exactly to the source used
18570 for compilation has been found on the path but it is hidden by another
18571 version of the same source that has been modified.
18575 @node Switches for gnatls
18576 @section Switches for @code{gnatls}
18579 @code{gnatls} recognizes the following switches:
18583 @cindex @option{--version} @command{gnatls}
18584 Display Copyright and version, then exit disregarding all other options.
18587 @cindex @option{--help} @command{gnatls}
18588 If @option{--version} was not used, display usage, then exit disregarding
18591 @item ^-a^/ALL_UNITS^
18592 @cindex @option{^-a^/ALL_UNITS^} (@code{gnatls})
18593 Consider all units, including those of the predefined Ada library.
18594 Especially useful with @option{^-d^/DEPENDENCIES^}.
18596 @item ^-d^/DEPENDENCIES^
18597 @cindex @option{^-d^/DEPENDENCIES^} (@code{gnatls})
18598 List sources from which specified units depend on.
18600 @item ^-h^/OUTPUT=OPTIONS^
18601 @cindex @option{^-h^/OUTPUT=OPTIONS^} (@code{gnatls})
18602 Output the list of options.
18604 @item ^-o^/OUTPUT=OBJECTS^
18605 @cindex @option{^-o^/OUTPUT=OBJECTS^} (@code{gnatls})
18606 Only output information about object files.
18608 @item ^-s^/OUTPUT=SOURCES^
18609 @cindex @option{^-s^/OUTPUT=SOURCES^} (@code{gnatls})
18610 Only output information about source files.
18612 @item ^-u^/OUTPUT=UNITS^
18613 @cindex @option{^-u^/OUTPUT=UNITS^} (@code{gnatls})
18614 Only output information about compilation units.
18616 @item ^-files^/FILES^=@var{file}
18617 @cindex @option{^-files^/FILES^} (@code{gnatls})
18618 Take as arguments the files listed in text file @var{file}.
18619 Text file @var{file} may contain empty lines that are ignored.
18620 Each nonempty line should contain the name of an existing file.
18621 Several such switches may be specified simultaneously.
18623 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18624 @itemx ^-aI^/SOURCE_SEARCH=^@var{dir}
18625 @itemx ^-I^/SEARCH=^@var{dir}
18626 @itemx ^-I-^/NOCURRENT_DIRECTORY^
18628 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatls})
18629 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatls})
18630 @cindex @option{^-I^/SEARCH^} (@code{gnatls})
18631 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatls})
18632 Source path manipulation. Same meaning as the equivalent @command{gnatmake}
18633 flags (@pxref{Switches for gnatmake}).
18635 @item --RTS=@var{rts-path}
18636 @cindex @option{--RTS} (@code{gnatls})
18637 Specifies the default location of the runtime library. Same meaning as the
18638 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
18640 @item ^-v^/OUTPUT=VERBOSE^
18641 @cindex @option{^-v^/OUTPUT=VERBOSE^} (@code{gnatls})
18642 Verbose mode. Output the complete source, object and project paths. Do not use
18643 the default column layout but instead use long format giving as much as
18644 information possible on each requested units, including special
18645 characteristics such as:
18648 @item Preelaborable
18649 The unit is preelaborable in the Ada sense.
18652 No elaboration code has been produced by the compiler for this unit.
18655 The unit is pure in the Ada sense.
18657 @item Elaborate_Body
18658 The unit contains a pragma Elaborate_Body.
18661 The unit contains a pragma Remote_Types.
18663 @item Shared_Passive
18664 The unit contains a pragma Shared_Passive.
18667 This unit is part of the predefined environment and cannot be modified
18670 @item Remote_Call_Interface
18671 The unit contains a pragma Remote_Call_Interface.
18677 @node Examples of gnatls Usage
18678 @section Example of @code{gnatls} Usage
18682 Example of using the verbose switch. Note how the source and
18683 object paths are affected by the -I switch.
18686 $ gnatls -v -I.. demo1.o
18688 GNATLS 5.03w (20041123-34)
18689 Copyright 1997-2004 Free Software Foundation, Inc.
18691 Source Search Path:
18692 <Current_Directory>
18694 /home/comar/local/adainclude/
18696 Object Search Path:
18697 <Current_Directory>
18699 /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/
18701 Project Search Path:
18702 <Current_Directory>
18703 /home/comar/local/lib/gnat/
18708 Kind => subprogram body
18709 Flags => No_Elab_Code
18710 Source => demo1.adb modified
18714 The following is an example of use of the dependency list.
18715 Note the use of the -s switch
18716 which gives a straight list of source files. This can be useful for
18717 building specialized scripts.
18720 $ gnatls -d demo2.o
18721 ./demo2.o demo2 OK demo2.adb
18727 $ gnatls -d -s -a demo1.o
18729 /home/comar/local/adainclude/ada.ads
18730 /home/comar/local/adainclude/a-finali.ads
18731 /home/comar/local/adainclude/a-filico.ads
18732 /home/comar/local/adainclude/a-stream.ads
18733 /home/comar/local/adainclude/a-tags.ads
18736 /home/comar/local/adainclude/gnat.ads
18737 /home/comar/local/adainclude/g-io.ads
18739 /home/comar/local/adainclude/system.ads
18740 /home/comar/local/adainclude/s-exctab.ads
18741 /home/comar/local/adainclude/s-finimp.ads
18742 /home/comar/local/adainclude/s-finroo.ads
18743 /home/comar/local/adainclude/s-secsta.ads
18744 /home/comar/local/adainclude/s-stalib.ads
18745 /home/comar/local/adainclude/s-stoele.ads
18746 /home/comar/local/adainclude/s-stratt.ads
18747 /home/comar/local/adainclude/s-tasoli.ads
18748 /home/comar/local/adainclude/s-unstyp.ads
18749 /home/comar/local/adainclude/unchconv.ads
18755 GNAT LIST /DEPENDENCIES /OUTPUT=SOURCES /ALL_UNITS DEMO1.ADB
18757 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]ada.ads
18758 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-finali.ads
18759 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-filico.ads
18760 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-stream.ads
18761 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-tags.ads
18765 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]gnat.ads
18766 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]g-io.ads
18768 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]system.ads
18769 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-exctab.ads
18770 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finimp.ads
18771 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finroo.ads
18772 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-secsta.ads
18773 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stalib.ads
18774 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stoele.ads
18775 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stratt.ads
18776 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-tasoli.ads
18777 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-unstyp.ads
18778 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]unchconv.ads
18782 @node Cleaning Up Using gnatclean
18783 @chapter Cleaning Up Using @code{gnatclean}
18785 @cindex Cleaning tool
18788 @code{gnatclean} is a tool that allows the deletion of files produced by the
18789 compiler, binder and linker, including ALI files, object files, tree files,
18790 expanded source files, library files, interface copy source files, binder
18791 generated files and executable files.
18794 * Running gnatclean::
18795 * Switches for gnatclean::
18796 @c * Examples of gnatclean Usage::
18799 @node Running gnatclean
18800 @section Running @code{gnatclean}
18803 The @code{gnatclean} command has the form:
18806 $ gnatclean switches @var{names}
18810 @var{names} is a list of source file names. Suffixes @code{.^ads^ADS^} and
18811 @code{^adb^ADB^} may be omitted. If a project file is specified using switch
18812 @code{^-P^/PROJECT_FILE=^}, then @var{names} may be completely omitted.
18815 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
18816 if switch @code{^-c^/COMPILER_FILES_ONLY^} is not specified, by the binder and
18817 the linker. In informative-only mode, specified by switch
18818 @code{^-n^/NODELETE^}, the list of files that would have been deleted in
18819 normal mode is listed, but no file is actually deleted.
18821 @node Switches for gnatclean
18822 @section Switches for @code{gnatclean}
18825 @code{gnatclean} recognizes the following switches:
18829 @cindex @option{--version} @command{gnatclean}
18830 Display Copyright and version, then exit disregarding all other options.
18833 @cindex @option{--help} @command{gnatclean}
18834 If @option{--version} was not used, display usage, then exit disregarding
18837 @item ^-c^/COMPILER_FILES_ONLY^
18838 @cindex @option{^-c^/COMPILER_FILES_ONLY^} (@code{gnatclean})
18839 Only attempt to delete the files produced by the compiler, not those produced
18840 by the binder or the linker. The files that are not to be deleted are library
18841 files, interface copy files, binder generated files and executable files.
18843 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
18844 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatclean})
18845 Indicate that ALI and object files should normally be found in directory
18848 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
18849 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatclean})
18850 When using project files, if some errors or warnings are detected during
18851 parsing and verbose mode is not in effect (no use of switch
18852 ^-v^/VERBOSE^), then error lines start with the full path name of the project
18853 file, rather than its simple file name.
18856 @cindex @option{^-h^/HELP^} (@code{gnatclean})
18857 Output a message explaining the usage of @code{^gnatclean^gnatclean^}.
18859 @item ^-n^/NODELETE^
18860 @cindex @option{^-n^/NODELETE^} (@code{gnatclean})
18861 Informative-only mode. Do not delete any files. Output the list of the files
18862 that would have been deleted if this switch was not specified.
18864 @item ^-P^/PROJECT_FILE=^@var{project}
18865 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatclean})
18866 Use project file @var{project}. Only one such switch can be used.
18867 When cleaning a project file, the files produced by the compilation of the
18868 immediate sources or inherited sources of the project files are to be
18869 deleted. This is not depending on the presence or not of executable names
18870 on the command line.
18873 @cindex @option{^-q^/QUIET^} (@code{gnatclean})
18874 Quiet output. If there are no errors, do not output anything, except in
18875 verbose mode (switch ^-v^/VERBOSE^) or in informative-only mode
18876 (switch ^-n^/NODELETE^).
18878 @item ^-r^/RECURSIVE^
18879 @cindex @option{^-r^/RECURSIVE^} (@code{gnatclean})
18880 When a project file is specified (using switch ^-P^/PROJECT_FILE=^),
18881 clean all imported and extended project files, recursively. If this switch
18882 is not specified, only the files related to the main project file are to be
18883 deleted. This switch has no effect if no project file is specified.
18885 @item ^-v^/VERBOSE^
18886 @cindex @option{^-v^/VERBOSE^} (@code{gnatclean})
18889 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
18890 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (@code{gnatclean})
18891 Indicates the verbosity of the parsing of GNAT project files.
18892 @xref{Switches Related to Project Files}.
18894 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
18895 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (@code{gnatclean})
18896 Indicates that external variable @var{name} has the value @var{value}.
18897 The Project Manager will use this value for occurrences of
18898 @code{external(name)} when parsing the project file.
18899 @xref{Switches Related to Project Files}.
18901 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18902 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatclean})
18903 When searching for ALI and object files, look in directory
18906 @item ^-I^/SEARCH=^@var{dir}
18907 @cindex @option{^-I^/SEARCH^} (@code{gnatclean})
18908 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}}.
18910 @item ^-I-^/NOCURRENT_DIRECTORY^
18911 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatclean})
18912 @cindex Source files, suppressing search
18913 Do not look for ALI or object files in the directory
18914 where @code{gnatclean} was invoked.
18918 @c @node Examples of gnatclean Usage
18919 @c @section Examples of @code{gnatclean} Usage
18922 @node GNAT and Libraries
18923 @chapter GNAT and Libraries
18924 @cindex Library, building, installing, using
18927 This chapter describes how to build and use libraries with GNAT, and also shows
18928 how to recompile the GNAT run-time library. You should be familiar with the
18929 Project Manager facility (@pxref{GNAT Project Manager}) before reading this
18933 * Introduction to Libraries in GNAT::
18934 * General Ada Libraries::
18935 * Stand-alone Ada Libraries::
18936 * Rebuilding the GNAT Run-Time Library::
18939 @node Introduction to Libraries in GNAT
18940 @section Introduction to Libraries in GNAT
18943 A library is, conceptually, a collection of objects which does not have its
18944 own main thread of execution, but rather provides certain services to the
18945 applications that use it. A library can be either statically linked with the
18946 application, in which case its code is directly included in the application,
18947 or, on platforms that support it, be dynamically linked, in which case
18948 its code is shared by all applications making use of this library.
18950 GNAT supports both types of libraries.
18951 In the static case, the compiled code can be provided in different ways. The
18952 simplest approach is to provide directly the set of objects resulting from
18953 compilation of the library source files. Alternatively, you can group the
18954 objects into an archive using whatever commands are provided by the operating
18955 system. For the latter case, the objects are grouped into a shared library.
18957 In the GNAT environment, a library has three types of components:
18963 @xref{The Ada Library Information Files}.
18965 Object files, an archive or a shared library.
18969 A GNAT library may expose all its source files, which is useful for
18970 documentation purposes. Alternatively, it may expose only the units needed by
18971 an external user to make use of the library. That is to say, the specs
18972 reflecting the library services along with all the units needed to compile
18973 those specs, which can include generic bodies or any body implementing an
18974 inlined routine. In the case of @emph{stand-alone libraries} those exposed
18975 units are called @emph{interface units} (@pxref{Stand-alone Ada Libraries}).
18977 All compilation units comprising an application, including those in a library,
18978 need to be elaborated in an order partially defined by Ada's semantics. GNAT
18979 computes the elaboration order from the @file{ALI} files and this is why they
18980 constitute a mandatory part of GNAT libraries.
18981 @emph{Stand-alone libraries} are the exception to this rule because a specific
18982 library elaboration routine is produced independently of the application(s)
18985 @node General Ada Libraries
18986 @section General Ada Libraries
18989 * Building a library::
18990 * Installing a library::
18991 * Using a library::
18994 @node Building a library
18995 @subsection Building a library
18998 The easiest way to build a library is to use the Project Manager,
18999 which supports a special type of project called a @emph{Library Project}
19000 (@pxref{Library Projects}).
19002 A project is considered a library project, when two project-level attributes
19003 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
19004 control different aspects of library configuration, additional optional
19005 project-level attributes can be specified:
19008 This attribute controls whether the library is to be static or dynamic
19010 @item Library_Version
19011 This attribute specifies the library version; this value is used
19012 during dynamic linking of shared libraries to determine if the currently
19013 installed versions of the binaries are compatible.
19015 @item Library_Options
19017 These attributes specify additional low-level options to be used during
19018 library generation, and redefine the actual application used to generate
19023 The GNAT Project Manager takes full care of the library maintenance task,
19024 including recompilation of the source files for which objects do not exist
19025 or are not up to date, assembly of the library archive, and installation of
19026 the library (i.e., copying associated source, object and @file{ALI} files
19027 to the specified location).
19029 Here is a simple library project file:
19030 @smallexample @c ada
19032 for Source_Dirs use ("src1", "src2");
19033 for Object_Dir use "obj";
19034 for Library_Name use "mylib";
19035 for Library_Dir use "lib";
19036 for Library_Kind use "dynamic";
19041 and the compilation command to build and install the library:
19043 @smallexample @c ada
19044 $ gnatmake -Pmy_lib
19048 It is not entirely trivial to perform manually all the steps required to
19049 produce a library. We recommend that you use the GNAT Project Manager
19050 for this task. In special cases where this is not desired, the necessary
19051 steps are discussed below.
19053 There are various possibilities for compiling the units that make up the
19054 library: for example with a Makefile (@pxref{Using the GNU make Utility}) or
19055 with a conventional script. For simple libraries, it is also possible to create
19056 a dummy main program which depends upon all the packages that comprise the
19057 interface of the library. This dummy main program can then be given to
19058 @command{gnatmake}, which will ensure that all necessary objects are built.
19060 After this task is accomplished, you should follow the standard procedure
19061 of the underlying operating system to produce the static or shared library.
19063 Here is an example of such a dummy program:
19064 @smallexample @c ada
19066 with My_Lib.Service1;
19067 with My_Lib.Service2;
19068 with My_Lib.Service3;
19069 procedure My_Lib_Dummy is
19077 Here are the generic commands that will build an archive or a shared library.
19080 # compiling the library
19081 $ gnatmake -c my_lib_dummy.adb
19083 # we don't need the dummy object itself
19084 $ rm my_lib_dummy.o my_lib_dummy.ali
19086 # create an archive with the remaining objects
19087 $ ar rc libmy_lib.a *.o
19088 # some systems may require "ranlib" to be run as well
19090 # or create a shared library
19091 $ gcc -shared -o libmy_lib.so *.o
19092 # some systems may require the code to have been compiled with -fPIC
19094 # remove the object files that are now in the library
19097 # Make the ALI files read-only so that gnatmake will not try to
19098 # regenerate the objects that are in the library
19103 Please note that the library must have a name of the form @file{lib@var{xxx}.a}
19104 or @file{lib@var{xxx}.so} (or @file{lib@var{xxx}.dll} on Windows) in order to
19105 be accessed by the directive @option{-l@var{xxx}} at link time.
19107 @node Installing a library
19108 @subsection Installing a library
19109 @cindex @code{ADA_PROJECT_PATH}
19110 @cindex @code{GPR_PROJECT_PATH}
19113 If you use project files, library installation is part of the library build
19114 process. Thus no further action is needed in order to make use of the
19115 libraries that are built as part of the general application build. A usable
19116 version of the library is installed in the directory specified by the
19117 @code{Library_Dir} attribute of the library project file.
19119 You may want to install a library in a context different from where the library
19120 is built. This situation arises with third party suppliers, who may want
19121 to distribute a library in binary form where the user is not expected to be
19122 able to recompile the library. The simplest option in this case is to provide
19123 a project file slightly different from the one used to build the library, by
19124 using the @code{externally_built} attribute. For instance, the project
19125 file used to build the library in the previous section can be changed into the
19126 following one when the library is installed:
19128 @smallexample @c projectfile
19130 for Source_Dirs use ("src1", "src2");
19131 for Library_Name use "mylib";
19132 for Library_Dir use "lib";
19133 for Library_Kind use "dynamic";
19134 for Externally_Built use "true";
19139 This project file assumes that the directories @file{src1},
19140 @file{src2}, and @file{lib} exist in
19141 the directory containing the project file. The @code{externally_built}
19142 attribute makes it clear to the GNAT builder that it should not attempt to
19143 recompile any of the units from this library. It allows the library provider to
19144 restrict the source set to the minimum necessary for clients to make use of the
19145 library as described in the first section of this chapter. It is the
19146 responsibility of the library provider to install the necessary sources, ALI
19147 files and libraries in the directories mentioned in the project file. For
19148 convenience, the user's library project file should be installed in a location
19149 that will be searched automatically by the GNAT
19150 builder. These are the directories referenced in the @env{GPR_PROJECT_PATH}
19151 environment variable (@pxref{Importing Projects}), and also the default GNAT
19152 library location that can be queried with @command{gnatls -v} and is usually of
19153 the form $gnat_install_root/lib/gnat.
19155 When project files are not an option, it is also possible, but not recommended,
19156 to install the library so that the sources needed to use the library are on the
19157 Ada source path and the ALI files & libraries be on the Ada Object path (see
19158 @ref{Search Paths and the Run-Time Library (RTL)}. Alternatively, the system
19159 administrator can place general-purpose libraries in the default compiler
19160 paths, by specifying the libraries' location in the configuration files
19161 @file{ada_source_path} and @file{ada_object_path}. These configuration files
19162 must be located in the GNAT installation tree at the same place as the gcc spec
19163 file. The location of the gcc spec file can be determined as follows:
19169 The configuration files mentioned above have a simple format: each line
19170 must contain one unique directory name.
19171 Those names are added to the corresponding path
19172 in their order of appearance in the file. The names can be either absolute
19173 or relative; in the latter case, they are relative to where theses files
19176 The files @file{ada_source_path} and @file{ada_object_path} might not be
19178 GNAT installation, in which case, GNAT will look for its run-time library in
19179 the directories @file{adainclude} (for the sources) and @file{adalib} (for the
19180 objects and @file{ALI} files). When the files exist, the compiler does not
19181 look in @file{adainclude} and @file{adalib}, and thus the
19182 @file{ada_source_path} file
19183 must contain the location for the GNAT run-time sources (which can simply
19184 be @file{adainclude}). In the same way, the @file{ada_object_path} file must
19185 contain the location for the GNAT run-time objects (which can simply
19188 You can also specify a new default path to the run-time library at compilation
19189 time with the switch @option{--RTS=rts-path}. You can thus choose / change
19190 the run-time library you want your program to be compiled with. This switch is
19191 recognized by @command{gcc}, @command{gnatmake}, @command{gnatbind},
19192 @command{gnatls}, @command{gnatfind} and @command{gnatxref}.
19194 It is possible to install a library before or after the standard GNAT
19195 library, by reordering the lines in the configuration files. In general, a
19196 library must be installed before the GNAT library if it redefines
19199 @node Using a library
19200 @subsection Using a library
19202 @noindent Once again, the project facility greatly simplifies the use of
19203 libraries. In this context, using a library is just a matter of adding a
19204 @code{with} clause in the user project. For instance, to make use of the
19205 library @code{My_Lib} shown in examples in earlier sections, you can
19208 @smallexample @c projectfile
19215 Even if you have a third-party, non-Ada library, you can still use GNAT's
19216 Project Manager facility to provide a wrapper for it. For example, the
19217 following project, when @code{with}ed by your main project, will link with the
19218 third-party library @file{liba.a}:
19220 @smallexample @c projectfile
19223 for Externally_Built use "true";
19224 for Source_Files use ();
19225 for Library_Dir use "lib";
19226 for Library_Name use "a";
19227 for Library_Kind use "static";
19231 This is an alternative to the use of @code{pragma Linker_Options}. It is
19232 especially interesting in the context of systems with several interdependent
19233 static libraries where finding a proper linker order is not easy and best be
19234 left to the tools having visibility over project dependence information.
19237 In order to use an Ada library manually, you need to make sure that this
19238 library is on both your source and object path
19239 (see @ref{Search Paths and the Run-Time Library (RTL)}
19240 and @ref{Search Paths for gnatbind}). Furthermore, when the objects are grouped
19241 in an archive or a shared library, you need to specify the desired
19242 library at link time.
19244 For example, you can use the library @file{mylib} installed in
19245 @file{/dir/my_lib_src} and @file{/dir/my_lib_obj} with the following commands:
19248 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \
19253 This can be expressed more simply:
19258 when the following conditions are met:
19261 @file{/dir/my_lib_src} has been added by the user to the environment
19262 variable @env{ADA_INCLUDE_PATH}, or by the administrator to the file
19263 @file{ada_source_path}
19265 @file{/dir/my_lib_obj} has been added by the user to the environment
19266 variable @env{ADA_OBJECTS_PATH}, or by the administrator to the file
19267 @file{ada_object_path}
19269 a pragma @code{Linker_Options} has been added to one of the sources.
19272 @smallexample @c ada
19273 pragma Linker_Options ("-lmy_lib");
19277 @node Stand-alone Ada Libraries
19278 @section Stand-alone Ada Libraries
19279 @cindex Stand-alone library, building, using
19282 * Introduction to Stand-alone Libraries::
19283 * Building a Stand-alone Library::
19284 * Creating a Stand-alone Library to be used in a non-Ada context::
19285 * Restrictions in Stand-alone Libraries::
19288 @node Introduction to Stand-alone Libraries
19289 @subsection Introduction to Stand-alone Libraries
19292 A Stand-alone Library (abbreviated ``SAL'') is a library that contains the
19294 elaborate the Ada units that are included in the library. In contrast with
19295 an ordinary library, which consists of all sources, objects and @file{ALI}
19297 library, a SAL may specify a restricted subset of compilation units
19298 to serve as a library interface. In this case, the fully
19299 self-sufficient set of files will normally consist of an objects
19300 archive, the sources of interface units' specs, and the @file{ALI}
19301 files of interface units.
19302 If an interface spec contains a generic unit or an inlined subprogram,
19304 source must also be provided; if the units that must be provided in the source
19305 form depend on other units, the source and @file{ALI} files of those must
19308 The main purpose of a SAL is to minimize the recompilation overhead of client
19309 applications when a new version of the library is installed. Specifically,
19310 if the interface sources have not changed, client applications do not need to
19311 be recompiled. If, furthermore, a SAL is provided in the shared form and its
19312 version, controlled by @code{Library_Version} attribute, is not changed,
19313 then the clients do not need to be relinked.
19315 SALs also allow the library providers to minimize the amount of library source
19316 text exposed to the clients. Such ``information hiding'' might be useful or
19317 necessary for various reasons.
19319 Stand-alone libraries are also well suited to be used in an executable whose
19320 main routine is not written in Ada.
19322 @node Building a Stand-alone Library
19323 @subsection Building a Stand-alone Library
19326 GNAT's Project facility provides a simple way of building and installing
19327 stand-alone libraries; see @ref{Stand-alone Library Projects}.
19328 To be a Stand-alone Library Project, in addition to the two attributes
19329 that make a project a Library Project (@code{Library_Name} and
19330 @code{Library_Dir}; see @ref{Library Projects}), the attribute
19331 @code{Library_Interface} must be defined. For example:
19333 @smallexample @c projectfile
19335 for Library_Dir use "lib_dir";
19336 for Library_Name use "dummy";
19337 for Library_Interface use ("int1", "int1.child");
19342 Attribute @code{Library_Interface} has a non-empty string list value,
19343 each string in the list designating a unit contained in an immediate source
19344 of the project file.
19346 When a Stand-alone Library is built, first the binder is invoked to build
19347 a package whose name depends on the library name
19348 (@file{^b~dummy.ads/b^B$DUMMY.ADS/B^} in the example above).
19349 This binder-generated package includes initialization and
19350 finalization procedures whose
19351 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
19353 above). The object corresponding to this package is included in the library.
19355 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
19356 calling of these procedures if a static SAL is built, or if a shared SAL
19358 with the project-level attribute @code{Library_Auto_Init} set to
19361 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
19362 (those that are listed in attribute @code{Library_Interface}) are copied to
19363 the Library Directory. As a consequence, only the Interface Units may be
19364 imported from Ada units outside of the library. If other units are imported,
19365 the binding phase will fail.
19367 The attribute @code{Library_Src_Dir} may be specified for a
19368 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
19369 single string value. Its value must be the path (absolute or relative to the
19370 project directory) of an existing directory. This directory cannot be the
19371 object directory or one of the source directories, but it can be the same as
19372 the library directory. The sources of the Interface
19373 Units of the library that are needed by an Ada client of the library will be
19374 copied to the designated directory, called the Interface Copy directory.
19375 These sources include the specs of the Interface Units, but they may also
19376 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
19377 are used, or when there is a generic unit in the spec. Before the sources
19378 are copied to the Interface Copy directory, an attempt is made to delete all
19379 files in the Interface Copy directory.
19381 Building stand-alone libraries by hand is somewhat tedious, but for those
19382 occasions when it is necessary here are the steps that you need to perform:
19385 Compile all library sources.
19388 Invoke the binder with the switch @option{-n} (No Ada main program),
19389 with all the @file{ALI} files of the interfaces, and
19390 with the switch @option{-L} to give specific names to the @code{init}
19391 and @code{final} procedures. For example:
19393 gnatbind -n int1.ali int2.ali -Lsal1
19397 Compile the binder generated file:
19403 Link the dynamic library with all the necessary object files,
19404 indicating to the linker the names of the @code{init} (and possibly
19405 @code{final}) procedures for automatic initialization (and finalization).
19406 The built library should be placed in a directory different from
19407 the object directory.
19410 Copy the @code{ALI} files of the interface to the library directory,
19411 add in this copy an indication that it is an interface to a SAL
19412 (i.e., add a word @option{SL} on the line in the @file{ALI} file that starts
19413 with letter ``P'') and make the modified copy of the @file{ALI} file
19418 Using SALs is not different from using other libraries
19419 (see @ref{Using a library}).
19421 @node Creating a Stand-alone Library to be used in a non-Ada context
19422 @subsection Creating a Stand-alone Library to be used in a non-Ada context
19425 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
19428 The only extra step required is to ensure that library interface subprograms
19429 are compatible with the main program, by means of @code{pragma Export}
19430 or @code{pragma Convention}.
19432 Here is an example of simple library interface for use with C main program:
19434 @smallexample @c ada
19435 package Interface is
19437 procedure Do_Something;
19438 pragma Export (C, Do_Something, "do_something");
19440 procedure Do_Something_Else;
19441 pragma Export (C, Do_Something_Else, "do_something_else");
19447 On the foreign language side, you must provide a ``foreign'' view of the
19448 library interface; remember that it should contain elaboration routines in
19449 addition to interface subprograms.
19451 The example below shows the content of @code{mylib_interface.h} (note
19452 that there is no rule for the naming of this file, any name can be used)
19454 /* the library elaboration procedure */
19455 extern void mylibinit (void);
19457 /* the library finalization procedure */
19458 extern void mylibfinal (void);
19460 /* the interface exported by the library */
19461 extern void do_something (void);
19462 extern void do_something_else (void);
19466 Libraries built as explained above can be used from any program, provided
19467 that the elaboration procedures (named @code{mylibinit} in the previous
19468 example) are called before the library services are used. Any number of
19469 libraries can be used simultaneously, as long as the elaboration
19470 procedure of each library is called.
19472 Below is an example of a C program that uses the @code{mylib} library.
19475 #include "mylib_interface.h"
19480 /* First, elaborate the library before using it */
19483 /* Main program, using the library exported entities */
19485 do_something_else ();
19487 /* Library finalization at the end of the program */
19494 Note that invoking any library finalization procedure generated by
19495 @code{gnatbind} shuts down the Ada run-time environment.
19497 finalization of all Ada libraries must be performed at the end of the program.
19498 No call to these libraries or to the Ada run-time library should be made
19499 after the finalization phase.
19501 @node Restrictions in Stand-alone Libraries
19502 @subsection Restrictions in Stand-alone Libraries
19505 The pragmas listed below should be used with caution inside libraries,
19506 as they can create incompatibilities with other Ada libraries:
19508 @item pragma @code{Locking_Policy}
19509 @item pragma @code{Queuing_Policy}
19510 @item pragma @code{Task_Dispatching_Policy}
19511 @item pragma @code{Unreserve_All_Interrupts}
19515 When using a library that contains such pragmas, the user must make sure
19516 that all libraries use the same pragmas with the same values. Otherwise,
19517 @code{Program_Error} will
19518 be raised during the elaboration of the conflicting
19519 libraries. The usage of these pragmas and its consequences for the user
19520 should therefore be well documented.
19522 Similarly, the traceback in the exception occurrence mechanism should be
19523 enabled or disabled in a consistent manner across all libraries.
19524 Otherwise, Program_Error will be raised during the elaboration of the
19525 conflicting libraries.
19527 If the @code{Version} or @code{Body_Version}
19528 attributes are used inside a library, then you need to
19529 perform a @code{gnatbind} step that specifies all @file{ALI} files in all
19530 libraries, so that version identifiers can be properly computed.
19531 In practice these attributes are rarely used, so this is unlikely
19532 to be a consideration.
19534 @node Rebuilding the GNAT Run-Time Library
19535 @section Rebuilding the GNAT Run-Time Library
19536 @cindex GNAT Run-Time Library, rebuilding
19537 @cindex Building the GNAT Run-Time Library
19538 @cindex Rebuilding the GNAT Run-Time Library
19539 @cindex Run-Time Library, rebuilding
19542 It may be useful to recompile the GNAT library in various contexts, the
19543 most important one being the use of partition-wide configuration pragmas
19544 such as @code{Normalize_Scalars}. A special Makefile called
19545 @code{Makefile.adalib} is provided to that effect and can be found in
19546 the directory containing the GNAT library. The location of this
19547 directory depends on the way the GNAT environment has been installed and can
19548 be determined by means of the command:
19555 The last entry in the object search path usually contains the
19556 gnat library. This Makefile contains its own documentation and in
19557 particular the set of instructions needed to rebuild a new library and
19560 @node Using the GNU make Utility
19561 @chapter Using the GNU @code{make} Utility
19565 This chapter offers some examples of makefiles that solve specific
19566 problems. It does not explain how to write a makefile (@pxref{Top,, GNU
19567 make, make, GNU @code{make}}), nor does it try to replace the
19568 @command{gnatmake} utility (@pxref{The GNAT Make Program gnatmake}).
19570 All the examples in this section are specific to the GNU version of
19571 make. Although @command{make} is a standard utility, and the basic language
19572 is the same, these examples use some advanced features found only in
19576 * Using gnatmake in a Makefile::
19577 * Automatically Creating a List of Directories::
19578 * Generating the Command Line Switches::
19579 * Overcoming Command Line Length Limits::
19582 @node Using gnatmake in a Makefile
19583 @section Using gnatmake in a Makefile
19588 Complex project organizations can be handled in a very powerful way by
19589 using GNU make combined with gnatmake. For instance, here is a Makefile
19590 which allows you to build each subsystem of a big project into a separate
19591 shared library. Such a makefile allows you to significantly reduce the link
19592 time of very big applications while maintaining full coherence at
19593 each step of the build process.
19595 The list of dependencies are handled automatically by
19596 @command{gnatmake}. The Makefile is simply used to call gnatmake in each of
19597 the appropriate directories.
19599 Note that you should also read the example on how to automatically
19600 create the list of directories
19601 (@pxref{Automatically Creating a List of Directories})
19602 which might help you in case your project has a lot of subdirectories.
19607 @font@heightrm=cmr8
19610 ## This Makefile is intended to be used with the following directory
19612 ## - The sources are split into a series of csc (computer software components)
19613 ## Each of these csc is put in its own directory.
19614 ## Their name are referenced by the directory names.
19615 ## They will be compiled into shared library (although this would also work
19616 ## with static libraries
19617 ## - The main program (and possibly other packages that do not belong to any
19618 ## csc is put in the top level directory (where the Makefile is).
19619 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
19620 ## \_ second_csc (sources) __ lib (will contain the library)
19622 ## Although this Makefile is build for shared library, it is easy to modify
19623 ## to build partial link objects instead (modify the lines with -shared and
19626 ## With this makefile, you can change any file in the system or add any new
19627 ## file, and everything will be recompiled correctly (only the relevant shared
19628 ## objects will be recompiled, and the main program will be re-linked).
19630 # The list of computer software component for your project. This might be
19631 # generated automatically.
19634 # Name of the main program (no extension)
19637 # If we need to build objects with -fPIC, uncomment the following line
19640 # The following variable should give the directory containing libgnat.so
19641 # You can get this directory through 'gnatls -v'. This is usually the last
19642 # directory in the Object_Path.
19645 # The directories for the libraries
19646 # (This macro expands the list of CSC to the list of shared libraries, you
19647 # could simply use the expanded form:
19648 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
19649 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
19651 $@{MAIN@}: objects $@{LIB_DIR@}
19652 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
19653 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
19656 # recompile the sources
19657 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
19659 # Note: In a future version of GNAT, the following commands will be simplified
19660 # by a new tool, gnatmlib
19662 mkdir -p $@{dir $@@ @}
19663 cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
19664 cd $@{dir $@@ @} && cp -f ../*.ali .
19666 # The dependencies for the modules
19667 # Note that we have to force the expansion of *.o, since in some cases
19668 # make won't be able to do it itself.
19669 aa/lib/libaa.so: $@{wildcard aa/*.o@}
19670 bb/lib/libbb.so: $@{wildcard bb/*.o@}
19671 cc/lib/libcc.so: $@{wildcard cc/*.o@}
19673 # Make sure all of the shared libraries are in the path before starting the
19676 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
19679 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
19680 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
19681 $@{RM@} $@{CSC_LIST:%=%/*.o@}
19682 $@{RM@} *.o *.ali $@{MAIN@}
19685 @node Automatically Creating a List of Directories
19686 @section Automatically Creating a List of Directories
19689 In most makefiles, you will have to specify a list of directories, and
19690 store it in a variable. For small projects, it is often easier to
19691 specify each of them by hand, since you then have full control over what
19692 is the proper order for these directories, which ones should be
19695 However, in larger projects, which might involve hundreds of
19696 subdirectories, it might be more convenient to generate this list
19699 The example below presents two methods. The first one, although less
19700 general, gives you more control over the list. It involves wildcard
19701 characters, that are automatically expanded by @command{make}. Its
19702 shortcoming is that you need to explicitly specify some of the
19703 organization of your project, such as for instance the directory tree
19704 depth, whether some directories are found in a separate tree, @enddots{}
19706 The second method is the most general one. It requires an external
19707 program, called @command{find}, which is standard on all Unix systems. All
19708 the directories found under a given root directory will be added to the
19714 @font@heightrm=cmr8
19717 # The examples below are based on the following directory hierarchy:
19718 # All the directories can contain any number of files
19719 # ROOT_DIRECTORY -> a -> aa -> aaa
19722 # -> b -> ba -> baa
19725 # This Makefile creates a variable called DIRS, that can be reused any time
19726 # you need this list (see the other examples in this section)
19728 # The root of your project's directory hierarchy
19732 # First method: specify explicitly the list of directories
19733 # This allows you to specify any subset of all the directories you need.
19736 DIRS := a/aa/ a/ab/ b/ba/
19739 # Second method: use wildcards
19740 # Note that the argument(s) to wildcard below should end with a '/'.
19741 # Since wildcards also return file names, we have to filter them out
19742 # to avoid duplicate directory names.
19743 # We thus use make's @code{dir} and @code{sort} functions.
19744 # It sets DIRs to the following value (note that the directories aaa and baa
19745 # are not given, unless you change the arguments to wildcard).
19746 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
19749 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
19750 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
19753 # Third method: use an external program
19754 # This command is much faster if run on local disks, avoiding NFS slowdowns.
19755 # This is the most complete command: it sets DIRs to the following value:
19756 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
19759 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
19763 @node Generating the Command Line Switches
19764 @section Generating the Command Line Switches
19767 Once you have created the list of directories as explained in the
19768 previous section (@pxref{Automatically Creating a List of Directories}),
19769 you can easily generate the command line arguments to pass to gnatmake.
19771 For the sake of completeness, this example assumes that the source path
19772 is not the same as the object path, and that you have two separate lists
19776 # see "Automatically creating a list of directories" to create
19781 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
19782 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
19785 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
19788 @node Overcoming Command Line Length Limits
19789 @section Overcoming Command Line Length Limits
19792 One problem that might be encountered on big projects is that many
19793 operating systems limit the length of the command line. It is thus hard to give
19794 gnatmake the list of source and object directories.
19796 This example shows how you can set up environment variables, which will
19797 make @command{gnatmake} behave exactly as if the directories had been
19798 specified on the command line, but have a much higher length limit (or
19799 even none on most systems).
19801 It assumes that you have created a list of directories in your Makefile,
19802 using one of the methods presented in
19803 @ref{Automatically Creating a List of Directories}.
19804 For the sake of completeness, we assume that the object
19805 path (where the ALI files are found) is different from the sources patch.
19807 Note a small trick in the Makefile below: for efficiency reasons, we
19808 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
19809 expanded immediately by @code{make}. This way we overcome the standard
19810 make behavior which is to expand the variables only when they are
19813 On Windows, if you are using the standard Windows command shell, you must
19814 replace colons with semicolons in the assignments to these variables.
19819 @font@heightrm=cmr8
19822 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECT_PATH.
19823 # This is the same thing as putting the -I arguments on the command line.
19824 # (the equivalent of using -aI on the command line would be to define
19825 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECT_PATH).
19826 # You can of course have different values for these variables.
19828 # Note also that we need to keep the previous values of these variables, since
19829 # they might have been set before running 'make' to specify where the GNAT
19830 # library is installed.
19832 # see "Automatically creating a list of directories" to create these
19838 space:=$@{empty@} $@{empty@}
19839 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
19840 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
19841 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
19842 ADA_OBJECT_PATH += $@{OBJECT_LIST@}
19843 export ADA_INCLUDE_PATH
19844 export ADA_OBJECT_PATH
19851 @node Memory Management Issues
19852 @chapter Memory Management Issues
19855 This chapter describes some useful memory pools provided in the GNAT library
19856 and in particular the GNAT Debug Pool facility, which can be used to detect
19857 incorrect uses of access values (including ``dangling references'').
19859 It also describes the @command{gnatmem} tool, which can be used to track down
19864 * Some Useful Memory Pools::
19865 * The GNAT Debug Pool Facility::
19867 * The gnatmem Tool::
19871 @node Some Useful Memory Pools
19872 @section Some Useful Memory Pools
19873 @findex Memory Pool
19874 @cindex storage, pool
19877 The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool
19878 storage pool. Allocations use the standard system call @code{malloc} while
19879 deallocations use the standard system call @code{free}. No reclamation is
19880 performed when the pool goes out of scope. For performance reasons, the
19881 standard default Ada allocators/deallocators do not use any explicit storage
19882 pools but if they did, they could use this storage pool without any change in
19883 behavior. That is why this storage pool is used when the user
19884 manages to make the default implicit allocator explicit as in this example:
19885 @smallexample @c ada
19886 type T1 is access Something;
19887 -- no Storage pool is defined for T2
19888 type T2 is access Something_Else;
19889 for T2'Storage_Pool use T1'Storage_Pool;
19890 -- the above is equivalent to
19891 for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;
19895 The @code{System.Pool_Local} package offers the Unbounded_Reclaim_Pool storage
19896 pool. The allocation strategy is similar to @code{Pool_Local}'s
19897 except that the all
19898 storage allocated with this pool is reclaimed when the pool object goes out of
19899 scope. This pool provides a explicit mechanism similar to the implicit one
19900 provided by several Ada 83 compilers for allocations performed through a local
19901 access type and whose purpose was to reclaim memory when exiting the
19902 scope of a given local access. As an example, the following program does not
19903 leak memory even though it does not perform explicit deallocation:
19905 @smallexample @c ada
19906 with System.Pool_Local;
19907 procedure Pooloc1 is
19908 procedure Internal is
19909 type A is access Integer;
19910 X : System.Pool_Local.Unbounded_Reclaim_Pool;
19911 for A'Storage_Pool use X;
19914 for I in 1 .. 50 loop
19919 for I in 1 .. 100 loop
19926 The @code{System.Pool_Size} package implements the Stack_Bounded_Pool used when
19927 @code{Storage_Size} is specified for an access type.
19928 The whole storage for the pool is
19929 allocated at once, usually on the stack at the point where the access type is
19930 elaborated. It is automatically reclaimed when exiting the scope where the
19931 access type is defined. This package is not intended to be used directly by the
19932 user and it is implicitly used for each such declaration:
19934 @smallexample @c ada
19935 type T1 is access Something;
19936 for T1'Storage_Size use 10_000;
19939 @node The GNAT Debug Pool Facility
19940 @section The GNAT Debug Pool Facility
19942 @cindex storage, pool, memory corruption
19945 The use of unchecked deallocation and unchecked conversion can easily
19946 lead to incorrect memory references. The problems generated by such
19947 references are usually difficult to tackle because the symptoms can be
19948 very remote from the origin of the problem. In such cases, it is
19949 very helpful to detect the problem as early as possible. This is the
19950 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
19952 In order to use the GNAT specific debugging pool, the user must
19953 associate a debug pool object with each of the access types that may be
19954 related to suspected memory problems. See Ada Reference Manual 13.11.
19955 @smallexample @c ada
19956 type Ptr is access Some_Type;
19957 Pool : GNAT.Debug_Pools.Debug_Pool;
19958 for Ptr'Storage_Pool use Pool;
19962 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
19963 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
19964 allow the user to redefine allocation and deallocation strategies. They
19965 also provide a checkpoint for each dereference, through the use of
19966 the primitive operation @code{Dereference} which is implicitly called at
19967 each dereference of an access value.
19969 Once an access type has been associated with a debug pool, operations on
19970 values of the type may raise four distinct exceptions,
19971 which correspond to four potential kinds of memory corruption:
19974 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
19976 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
19978 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
19980 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage }
19984 For types associated with a Debug_Pool, dynamic allocation is performed using
19985 the standard GNAT allocation routine. References to all allocated chunks of
19986 memory are kept in an internal dictionary. Several deallocation strategies are
19987 provided, whereupon the user can choose to release the memory to the system,
19988 keep it allocated for further invalid access checks, or fill it with an easily
19989 recognizable pattern for debug sessions. The memory pattern is the old IBM
19990 hexadecimal convention: @code{16#DEADBEEF#}.
19992 See the documentation in the file g-debpoo.ads for more information on the
19993 various strategies.
19995 Upon each dereference, a check is made that the access value denotes a
19996 properly allocated memory location. Here is a complete example of use of
19997 @code{Debug_Pools}, that includes typical instances of memory corruption:
19998 @smallexample @c ada
20002 with Gnat.Io; use Gnat.Io;
20003 with Unchecked_Deallocation;
20004 with Unchecked_Conversion;
20005 with GNAT.Debug_Pools;
20006 with System.Storage_Elements;
20007 with Ada.Exceptions; use Ada.Exceptions;
20008 procedure Debug_Pool_Test is
20010 type T is access Integer;
20011 type U is access all T;
20013 P : GNAT.Debug_Pools.Debug_Pool;
20014 for T'Storage_Pool use P;
20016 procedure Free is new Unchecked_Deallocation (Integer, T);
20017 function UC is new Unchecked_Conversion (U, T);
20020 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
20030 Put_Line (Integer'Image(B.all));
20032 when E : others => Put_Line ("raised: " & Exception_Name (E));
20037 when E : others => Put_Line ("raised: " & Exception_Name (E));
20041 Put_Line (Integer'Image(B.all));
20043 when E : others => Put_Line ("raised: " & Exception_Name (E));
20048 when E : others => Put_Line ("raised: " & Exception_Name (E));
20051 end Debug_Pool_Test;
20055 The debug pool mechanism provides the following precise diagnostics on the
20056 execution of this erroneous program:
20059 Total allocated bytes : 0
20060 Total deallocated bytes : 0
20061 Current Water Mark: 0
20065 Total allocated bytes : 8
20066 Total deallocated bytes : 0
20067 Current Water Mark: 8
20070 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
20071 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
20072 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
20073 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
20075 Total allocated bytes : 8
20076 Total deallocated bytes : 4
20077 Current Water Mark: 4
20082 @node The gnatmem Tool
20083 @section The @command{gnatmem} Tool
20087 The @code{gnatmem} utility monitors dynamic allocation and
20088 deallocation activity in a program, and displays information about
20089 incorrect deallocations and possible sources of memory leaks.
20090 It is designed to work in association with a static runtime library
20091 only and in this context provides three types of information:
20094 General information concerning memory management, such as the total
20095 number of allocations and deallocations, the amount of allocated
20096 memory and the high water mark, i.e.@: the largest amount of allocated
20097 memory in the course of program execution.
20100 Backtraces for all incorrect deallocations, that is to say deallocations
20101 which do not correspond to a valid allocation.
20104 Information on each allocation that is potentially the origin of a memory
20109 * Running gnatmem::
20110 * Switches for gnatmem::
20111 * Example of gnatmem Usage::
20114 @node Running gnatmem
20115 @subsection Running @code{gnatmem}
20118 @code{gnatmem} makes use of the output created by the special version of
20119 allocation and deallocation routines that record call information. This
20120 allows to obtain accurate dynamic memory usage history at a minimal cost to
20121 the execution speed. Note however, that @code{gnatmem} is not supported on
20122 all platforms (currently, it is supported on AIX, HP-UX, GNU/Linux,
20123 Solaris and Windows NT/2000/XP (x86).
20126 The @code{gnatmem} command has the form
20129 $ gnatmem @ovar{switches} user_program
20133 The program must have been linked with the instrumented version of the
20134 allocation and deallocation routines. This is done by linking with the
20135 @file{libgmem.a} library. For correct symbolic backtrace information,
20136 the user program should be compiled with debugging options
20137 (see @ref{Switches for gcc}). For example to build @file{my_program}:
20140 $ gnatmake -g my_program -largs -lgmem
20144 As library @file{libgmem.a} contains an alternate body for package
20145 @code{System.Memory}, @file{s-memory.adb} should not be compiled and linked
20146 when an executable is linked with library @file{libgmem.a}. It is then not
20147 recommended to use @command{gnatmake} with switch @option{^-a^/ALL_FILES^}.
20150 When @file{my_program} is executed, the file @file{gmem.out} is produced.
20151 This file contains information about all allocations and deallocations
20152 performed by the program. It is produced by the instrumented allocations and
20153 deallocations routines and will be used by @code{gnatmem}.
20155 In order to produce symbolic backtrace information for allocations and
20156 deallocations performed by the GNAT run-time library, you need to use a
20157 version of that library that has been compiled with the @option{-g} switch
20158 (see @ref{Rebuilding the GNAT Run-Time Library}).
20160 Gnatmem must be supplied with the @file{gmem.out} file and the executable to
20161 examine. If the location of @file{gmem.out} file was not explicitly supplied by
20162 @option{-i} switch, gnatmem will assume that this file can be found in the
20163 current directory. For example, after you have executed @file{my_program},
20164 @file{gmem.out} can be analyzed by @code{gnatmem} using the command:
20167 $ gnatmem my_program
20171 This will produce the output with the following format:
20173 *************** debut cc
20175 $ gnatmem my_program
20179 Total number of allocations : 45
20180 Total number of deallocations : 6
20181 Final Water Mark (non freed mem) : 11.29 Kilobytes
20182 High Water Mark : 11.40 Kilobytes
20187 Allocation Root # 2
20188 -------------------
20189 Number of non freed allocations : 11
20190 Final Water Mark (non freed mem) : 1.16 Kilobytes
20191 High Water Mark : 1.27 Kilobytes
20193 my_program.adb:23 my_program.alloc
20199 The first block of output gives general information. In this case, the
20200 Ada construct ``@code{@b{new}}'' was executed 45 times, and only 6 calls to an
20201 Unchecked_Deallocation routine occurred.
20204 Subsequent paragraphs display information on all allocation roots.
20205 An allocation root is a specific point in the execution of the program
20206 that generates some dynamic allocation, such as a ``@code{@b{new}}''
20207 construct. This root is represented by an execution backtrace (or subprogram
20208 call stack). By default the backtrace depth for allocations roots is 1, so
20209 that a root corresponds exactly to a source location. The backtrace can
20210 be made deeper, to make the root more specific.
20212 @node Switches for gnatmem
20213 @subsection Switches for @code{gnatmem}
20216 @code{gnatmem} recognizes the following switches:
20221 @cindex @option{-q} (@code{gnatmem})
20222 Quiet. Gives the minimum output needed to identify the origin of the
20223 memory leaks. Omits statistical information.
20226 @cindex @var{N} (@code{gnatmem})
20227 N is an integer literal (usually between 1 and 10) which controls the
20228 depth of the backtraces defining allocation root. The default value for
20229 N is 1. The deeper the backtrace, the more precise the localization of
20230 the root. Note that the total number of roots can depend on this
20231 parameter. This parameter must be specified @emph{before} the name of the
20232 executable to be analyzed, to avoid ambiguity.
20235 @cindex @option{-b} (@code{gnatmem})
20236 This switch has the same effect as just depth parameter.
20238 @item -i @var{file}
20239 @cindex @option{-i} (@code{gnatmem})
20240 Do the @code{gnatmem} processing starting from @file{file}, rather than
20241 @file{gmem.out} in the current directory.
20244 @cindex @option{-m} (@code{gnatmem})
20245 This switch causes @code{gnatmem} to mask the allocation roots that have less
20246 than n leaks. The default value is 1. Specifying the value of 0 will allow to
20247 examine even the roots that didn't result in leaks.
20250 @cindex @option{-s} (@code{gnatmem})
20251 This switch causes @code{gnatmem} to sort the allocation roots according to the
20252 specified order of sort criteria, each identified by a single letter. The
20253 currently supported criteria are @code{n, h, w} standing respectively for
20254 number of unfreed allocations, high watermark, and final watermark
20255 corresponding to a specific root. The default order is @code{nwh}.
20259 @node Example of gnatmem Usage
20260 @subsection Example of @code{gnatmem} Usage
20263 The following example shows the use of @code{gnatmem}
20264 on a simple memory-leaking program.
20265 Suppose that we have the following Ada program:
20267 @smallexample @c ada
20270 with Unchecked_Deallocation;
20271 procedure Test_Gm is
20273 type T is array (1..1000) of Integer;
20274 type Ptr is access T;
20275 procedure Free is new Unchecked_Deallocation (T, Ptr);
20278 procedure My_Alloc is
20283 procedure My_DeAlloc is
20291 for I in 1 .. 5 loop
20292 for J in I .. 5 loop
20303 The program needs to be compiled with debugging option and linked with
20304 @code{gmem} library:
20307 $ gnatmake -g test_gm -largs -lgmem
20311 Then we execute the program as usual:
20318 Then @code{gnatmem} is invoked simply with
20324 which produces the following output (result may vary on different platforms):
20329 Total number of allocations : 18
20330 Total number of deallocations : 5
20331 Final Water Mark (non freed mem) : 53.00 Kilobytes
20332 High Water Mark : 56.90 Kilobytes
20334 Allocation Root # 1
20335 -------------------
20336 Number of non freed allocations : 11
20337 Final Water Mark (non freed mem) : 42.97 Kilobytes
20338 High Water Mark : 46.88 Kilobytes
20340 test_gm.adb:11 test_gm.my_alloc
20342 Allocation Root # 2
20343 -------------------
20344 Number of non freed allocations : 1
20345 Final Water Mark (non freed mem) : 10.02 Kilobytes
20346 High Water Mark : 10.02 Kilobytes
20348 s-secsta.adb:81 system.secondary_stack.ss_init
20350 Allocation Root # 3
20351 -------------------
20352 Number of non freed allocations : 1
20353 Final Water Mark (non freed mem) : 12 Bytes
20354 High Water Mark : 12 Bytes
20356 s-secsta.adb:181 system.secondary_stack.ss_init
20360 Note that the GNAT run time contains itself a certain number of
20361 allocations that have no corresponding deallocation,
20362 as shown here for root #2 and root
20363 #3. This is a normal behavior when the number of non-freed allocations
20364 is one, it allocates dynamic data structures that the run time needs for
20365 the complete lifetime of the program. Note also that there is only one
20366 allocation root in the user program with a single line back trace:
20367 test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the
20368 program shows that 'My_Alloc' is called at 2 different points in the
20369 source (line 21 and line 24). If those two allocation roots need to be
20370 distinguished, the backtrace depth parameter can be used:
20373 $ gnatmem 3 test_gm
20377 which will give the following output:
20382 Total number of allocations : 18
20383 Total number of deallocations : 5
20384 Final Water Mark (non freed mem) : 53.00 Kilobytes
20385 High Water Mark : 56.90 Kilobytes
20387 Allocation Root # 1
20388 -------------------
20389 Number of non freed allocations : 10
20390 Final Water Mark (non freed mem) : 39.06 Kilobytes
20391 High Water Mark : 42.97 Kilobytes
20393 test_gm.adb:11 test_gm.my_alloc
20394 test_gm.adb:24 test_gm
20395 b_test_gm.c:52 main
20397 Allocation Root # 2
20398 -------------------
20399 Number of non freed allocations : 1
20400 Final Water Mark (non freed mem) : 10.02 Kilobytes
20401 High Water Mark : 10.02 Kilobytes
20403 s-secsta.adb:81 system.secondary_stack.ss_init
20404 s-secsta.adb:283 <system__secondary_stack___elabb>
20405 b_test_gm.c:33 adainit
20407 Allocation Root # 3
20408 -------------------
20409 Number of non freed allocations : 1
20410 Final Water Mark (non freed mem) : 3.91 Kilobytes
20411 High Water Mark : 3.91 Kilobytes
20413 test_gm.adb:11 test_gm.my_alloc
20414 test_gm.adb:21 test_gm
20415 b_test_gm.c:52 main
20417 Allocation Root # 4
20418 -------------------
20419 Number of non freed allocations : 1
20420 Final Water Mark (non freed mem) : 12 Bytes
20421 High Water Mark : 12 Bytes
20423 s-secsta.adb:181 system.secondary_stack.ss_init
20424 s-secsta.adb:283 <system__secondary_stack___elabb>
20425 b_test_gm.c:33 adainit
20429 The allocation root #1 of the first example has been split in 2 roots #1
20430 and #3 thanks to the more precise associated backtrace.
20434 @node Stack Related Facilities
20435 @chapter Stack Related Facilities
20438 This chapter describes some useful tools associated with stack
20439 checking and analysis. In
20440 particular, it deals with dynamic and static stack usage measurements.
20443 * Stack Overflow Checking::
20444 * Static Stack Usage Analysis::
20445 * Dynamic Stack Usage Analysis::
20448 @node Stack Overflow Checking
20449 @section Stack Overflow Checking
20450 @cindex Stack Overflow Checking
20451 @cindex -fstack-check
20454 For most operating systems, @command{gcc} does not perform stack overflow
20455 checking by default. This means that if the main environment task or
20456 some other task exceeds the available stack space, then unpredictable
20457 behavior will occur. Most native systems offer some level of protection by
20458 adding a guard page at the end of each task stack. This mechanism is usually
20459 not enough for dealing properly with stack overflow situations because
20460 a large local variable could ``jump'' above the guard page.
20461 Furthermore, when the
20462 guard page is hit, there may not be any space left on the stack for executing
20463 the exception propagation code. Enabling stack checking avoids
20466 To activate stack checking, compile all units with the gcc option
20467 @option{-fstack-check}. For example:
20470 gcc -c -fstack-check package1.adb
20474 Units compiled with this option will generate extra instructions to check
20475 that any use of the stack (for procedure calls or for declaring local
20476 variables in declare blocks) does not exceed the available stack space.
20477 If the space is exceeded, then a @code{Storage_Error} exception is raised.
20479 For declared tasks, the stack size is controlled by the size
20480 given in an applicable @code{Storage_Size} pragma or by the value specified
20481 at bind time with @option{-d} (@pxref{Switches for gnatbind}) or is set to
20482 the default size as defined in the GNAT runtime otherwise.
20484 For the environment task, the stack size depends on
20485 system defaults and is unknown to the compiler. Stack checking
20486 may still work correctly if a fixed
20487 size stack is allocated, but this cannot be guaranteed.
20489 To ensure that a clean exception is signalled for stack
20490 overflow, set the environment variable
20491 @env{GNAT_STACK_LIMIT} to indicate the maximum
20492 stack area that can be used, as in:
20493 @cindex GNAT_STACK_LIMIT
20496 SET GNAT_STACK_LIMIT 1600
20500 The limit is given in kilobytes, so the above declaration would
20501 set the stack limit of the environment task to 1.6 megabytes.
20502 Note that the only purpose of this usage is to limit the amount
20503 of stack used by the environment task. If it is necessary to
20504 increase the amount of stack for the environment task, then this
20505 is an operating systems issue, and must be addressed with the
20506 appropriate operating systems commands.
20509 To have a fixed size stack in the environment task, the stack must be put
20510 in the P0 address space and its size specified. Use these switches to
20514 gnatmake my_progs -largs "-Wl,--opt=STACK=4000,/p0image"
20518 The quotes are required to keep case. The number after @samp{STACK=} is the
20519 size of the environmental task stack in pagelets (512 bytes). In this example
20520 the stack size is about 2 megabytes.
20523 A consequence of the @option{/p0image} qualifier is also to makes RMS buffers
20524 be placed in P0 space. Refer to @cite{HP OpenVMS Linker Utility Manual} for
20525 more details about the @option{/p0image} qualifier and the @option{stack}
20529 @node Static Stack Usage Analysis
20530 @section Static Stack Usage Analysis
20531 @cindex Static Stack Usage Analysis
20532 @cindex -fstack-usage
20535 A unit compiled with @option{-fstack-usage} will generate an extra file
20537 the maximum amount of stack used, on a per-function basis.
20538 The file has the same
20539 basename as the target object file with a @file{.su} extension.
20540 Each line of this file is made up of three fields:
20544 The name of the function.
20548 One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
20551 The second field corresponds to the size of the known part of the function
20554 The qualifier @code{static} means that the function frame size
20556 It usually means that all local variables have a static size.
20557 In this case, the second field is a reliable measure of the function stack
20560 The qualifier @code{dynamic} means that the function frame size is not static.
20561 It happens mainly when some local variables have a dynamic size. When this
20562 qualifier appears alone, the second field is not a reliable measure
20563 of the function stack analysis. When it is qualified with @code{bounded}, it
20564 means that the second field is a reliable maximum of the function stack
20567 @node Dynamic Stack Usage Analysis
20568 @section Dynamic Stack Usage Analysis
20571 It is possible to measure the maximum amount of stack used by a task, by
20572 adding a switch to @command{gnatbind}, as:
20575 $ gnatbind -u0 file
20579 With this option, at each task termination, its stack usage is output on
20581 It is not always convenient to output the stack usage when the program
20582 is still running. Hence, it is possible to delay this output until program
20583 termination. for a given number of tasks specified as the argument of the
20584 @option{-u} option. For instance:
20587 $ gnatbind -u100 file
20591 will buffer the stack usage information of the first 100 tasks to terminate and
20592 output this info at program termination. Results are displayed in four
20596 Index | Task Name | Stack Size | Stack Usage [Value +/- Variation]
20603 is a number associated with each task.
20606 is the name of the task analyzed.
20609 is the maximum size for the stack.
20612 is the measure done by the stack analyzer. In order to prevent overflow, the stack
20613 is not entirely analyzed, and it's not possible to know exactly how
20614 much has actually been used. The report thus contains the theoretical stack usage
20615 (Value) and the possible variation (Variation) around this value.
20620 The environment task stack, e.g., the stack that contains the main unit, is
20621 only processed when the environment variable GNAT_STACK_LIMIT is set.
20624 @c *********************************
20626 @c *********************************
20627 @node Verifying Properties Using gnatcheck
20628 @chapter Verifying Properties Using @command{gnatcheck}
20630 @cindex @command{gnatcheck}
20633 The @command{gnatcheck} tool is an ASIS-based utility that checks properties
20634 of Ada source files according to a given set of semantic rules.
20637 In order to check compliance with a given rule, @command{gnatcheck} has to
20638 semantically analyze the Ada sources.
20639 Therefore, checks can only be performed on
20640 legal Ada units. Moreover, when a unit depends semantically upon units located
20641 outside the current directory, the source search path has to be provided when
20642 calling @command{gnatcheck}, either through a specified project file or
20643 through @command{gnatcheck} switches as described below.
20645 A number of rules are predefined in @command{gnatcheck} and are described
20646 later in this chapter.
20647 You can also add new rules, by modifying the @command{gnatcheck} code and
20648 rebuilding the tool. In order to add a simple rule making some local checks,
20649 a small amount of straightforward ASIS-based programming is usually needed.
20651 Project support for @command{gnatcheck} is provided by the GNAT
20652 driver (see @ref{The GNAT Driver and Project Files}).
20654 Invoking @command{gnatcheck} on the command line has the form:
20657 $ gnatcheck @ovar{switches} @{@var{filename}@}
20658 @r{[}^-files^/FILES^=@{@var{arg_list_filename}@}@r{]}
20659 @r{[}-cargs @var{gcc_switches}@r{]} @r{[}-rules @var{rule_options}@r{]}
20666 @var{switches} specify the general tool options
20669 Each @var{filename} is the name (including the extension) of a source
20670 file to process. ``Wildcards'' are allowed, and
20671 the file name may contain path information.
20674 Each @var{arg_list_filename} is the name (including the extension) of a text
20675 file containing the names of the source files to process, separated by spaces
20679 @var{gcc_switches} is a list of switches for
20680 @command{gcc}. They will be passed on to all compiler invocations made by
20681 @command{gnatcheck} to generate the ASIS trees. Here you can provide
20682 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
20683 and use the @option{-gnatec} switch to set the configuration file.
20686 @var{rule_options} is a list of options for controlling a set of
20687 rules to be checked by @command{gnatcheck} (@pxref{gnatcheck Rule Options}).
20691 Either a @file{@var{filename}} or an @file{@var{arg_list_filename}} must be supplied.
20694 * Format of the Report File::
20695 * General gnatcheck Switches::
20696 * gnatcheck Rule Options::
20697 * Adding the Results of Compiler Checks to gnatcheck Output::
20698 * Project-Wide Checks::
20699 * Predefined Rules::
20702 @node Format of the Report File
20703 @section Format of the Report File
20704 @cindex Report file (for @code{gnatcheck})
20707 The @command{gnatcheck} tool outputs on @file{stdout} all messages concerning
20709 It also creates a text file that
20710 contains the complete report of the last gnatcheck run. By default this file is
20711 named named @file{^gnatcheck.out^GNATCHECK.OUT^} and it is located in the current
20712 directory, @option{^-o^/OUTPUT^} option can be used to change the name and/or
20713 location of the report file. This report contains:
20715 @item a list of the Ada source files being checked,
20716 @item a list of enabled and disabled rules,
20717 @item a list of the diagnostic messages, ordered in three different ways
20718 and collected in three separate
20719 sections. Section 1 contains the raw list of diagnostic messages. It
20720 corresponds to the output going to @file{stdout}. Section 2 contains
20721 messages ordered by rules.
20722 Section 3 contains messages ordered by source files.
20725 @node General gnatcheck Switches
20726 @section General @command{gnatcheck} Switches
20729 The following switches control the general @command{gnatcheck} behavior
20733 @cindex @option{^-a^/ALL^} (@command{gnatcheck})
20735 Process all units including those with read-only ALI files such as
20736 those from GNAT Run-Time library.
20740 @cindex @option{-d} (@command{gnatcheck})
20745 @cindex @option{-dd} (@command{gnatcheck})
20747 Progress indicator mode (for use in GPS)
20750 @cindex @option{^-h^/HELP^} (@command{gnatcheck})
20752 List the predefined and user-defined rules. For more details see
20753 @ref{Predefined Rules}.
20755 @cindex @option{^-l^/LOCS^} (@command{gnatcheck})
20757 Use full source locations references in the report file. For a construct from
20758 a generic instantiation a full source location is a chain from the location
20759 of this construct in the generic unit to the place where this unit is
20762 @cindex @option{^-log^/LOG^} (@command{gnatcheck})
20764 Duplicate all the output sent to Stderr into a log file. The log file is
20765 named @var{gnatcheck.log} and is located in the current directory.
20767 @cindex @option{^-m^/DIAGNOSTIC_LIMIT^} (@command{gnatcheck})
20768 @item ^-m@i{nnn}^/DIAGNOSTIC_LIMIT=@i{nnn}^
20769 Maximum number of diagnoses to be sent to Stdout, @i{nnn} from o@dots{}1000,
20770 the default value is 500. Zero means that there is no limitation on
20771 the number of diagnostic messages to be printed into Stdout.
20773 @cindex @option{^-q^/QUIET^} (@command{gnatcheck})
20775 Quiet mode. All the diagnoses about rule violations are placed in the
20776 @command{gnatcheck} report file only, without duplicating in @file{stdout}.
20778 @cindex @option{^-s^/SHORT^} (@command{gnatcheck})
20780 Short format of the report file (no version information, no list of applied
20781 rules, no list of checked sources is included)
20783 @cindex @option{^-s1^/COMPILER_STYLE^} (@command{gnatcheck})
20784 @item ^-s1^/COMPILER_STYLE^
20785 Include the compiler-style section in the report file
20787 @cindex @option{^-s2^/BY_RULES^} (@command{gnatcheck})
20788 @item ^-s2^/BY_RULES^
20789 Include the section containing diagnoses ordered by rules in the report file
20791 @cindex @option{^-s3^/BY_FILES_BY_RULES^} (@command{gnatcheck})
20792 @item ^-s3^/BY_FILES_BY_RULES^
20793 Include the section containing diagnoses ordered by files and then by rules
20796 @cindex @option{^-t^/TIME^} (@command{gnatcheck})
20798 Print out execution time.
20800 @cindex @option{^-v^/VERBOSE^} (@command{gnatcheck})
20801 @item ^-v^/VERBOSE^
20802 Verbose mode; @command{gnatcheck} generates version information and then
20803 a trace of sources being processed.
20805 @cindex @option{^-o ^/OUTPUT^} (@command{gnatcheck})
20806 @item ^-o ^/OUTPUT=^@var{report_file}
20807 Set name of report file file to @var{report_file} .
20812 Note that if any of the options @option{^-s1^/COMPILER_STYLE^},
20813 @option{^-s2^/BY_RULES^} or
20814 @option{^-s3^/BY_FILES_BY_RULES^} is specified,
20815 then the @command{gnatcheck} report file will only contain sections
20816 explicitly denoted by these options.
20818 @node gnatcheck Rule Options
20819 @section @command{gnatcheck} Rule Options
20822 The following options control the processing performed by
20823 @command{gnatcheck}.
20826 @cindex @option{+ALL} (@command{gnatcheck})
20828 Turn all the rule checks ON.
20830 @cindex @option{-ALL} (@command{gnatcheck})
20832 Turn all the rule checks OFF.
20834 @cindex @option{+R} (@command{gnatcheck})
20835 @item +R@var{rule_id}@r{[}:@var{param}@r{]}
20836 Turn on the check for a specified rule with the specified parameter, if any.
20837 @var{rule_id} must be the identifier of one of the currently implemented rules
20838 (use @option{^-h^/HELP^} for the list of implemented rules). Rule identifiers
20839 are not case-sensitive. The @var{param} item must
20840 be a string representing a valid parameter(s) for the specified rule.
20841 If it contains any space characters then this string must be enclosed in
20844 @cindex @option{-R} (@command{gnatcheck})
20845 @item -R@var{rule_id}@r{[}:@var{param}@r{]}
20846 Turn off the check for a specified rule with the specified parameter, if any.
20848 @cindex @option{-from} (@command{gnatcheck})
20849 @item -from=@var{rule_option_filename}
20850 Read the rule options from the text file @var{rule_option_filename}, referred as
20851 ``rule file'' below.
20856 The default behavior is that all the rule checks are disabled.
20858 A rule file is a text file containing a set of rule options.
20859 @cindex Rule file (for @code{gnatcheck})
20860 The file may contain empty lines and Ada-style comments (comment
20861 lines and end-of-line comments). The rule file has free format; that is,
20862 you do not have to start a new rule option on a new line.
20864 A rule file may contain other @option{-from=@var{rule_option_filename}}
20865 options, each such option being replaced with the content of the
20866 corresponding rule file during the rule files processing. In case a
20867 cycle is detected (that is, @file{@var{rule_file_1}} reads rule options
20868 from @file{@var{rule_file_2}}, and @file{@var{rule_file_2}} reads
20869 (directly or indirectly) rule options from @file{@var{rule_file_1}}),
20870 the processing of rule files is interrupted and a part of their content
20874 @node Adding the Results of Compiler Checks to gnatcheck Output
20875 @section Adding the Results of Compiler Checks to @command{gnatcheck} Output
20878 The @command{gnatcheck} tool can include in the generated diagnostic messages
20880 the report file the results of the checks performed by the compiler. Though
20881 disabled by default, this effect may be obtained by using @option{+R} with
20882 the following rule identifiers and parameters:
20886 To record restrictions violations (that are performed by the compiler if the
20887 pragma @code{Restrictions} or @code{Restriction_Warnings} are given),
20889 @code{Restrictions} with the same parameters as pragma
20890 @code{Restrictions} or @code{Restriction_Warnings}.
20893 To record compiler style checks(@pxref{Style Checking}), use the rule named
20894 @code{Style_Checks}. A parameter of this rule can be either @code{All_Checks},
20895 which enables all the standard style checks that corresponds to @option{-gnatyy}
20896 GNAT style check option, or a string that has exactly the same
20897 structure and semantics as the @code{string_LITERAL} parameter of GNAT pragma
20898 @code{Style_Checks} (for further information about this pragma,
20899 @pxref{Pragma Style_Checks,,, gnat_rm, GNAT Reference Manual}). For example,
20900 @code{+RStyle_Checks:O} rule option activates and adds to @command{gnatcheck}
20901 output the compiler style check that corresponds to
20902 @code{-gnatyO} style check option.
20905 To record compiler warnings (@pxref{Warning Message Control}), use the rule
20906 named @code{Warnings} with a parameter that is a valid
20907 @i{static_string_expression} argument of GNAT pragma @code{Warnings}
20908 (for further information about this pragma, @pxref{Pragma Warnings,,,
20909 gnat_rm, GNAT Reference Manual}). Note, that in case of gnatcheck
20910 's' parameter, that corresponds to the GNAT @option{-gnatws} option, disables
20911 all the specific warnings, but not suppresses the warning mode,
20912 and 'e' parameter, corresponding to @option{-gnatwe} that means
20913 "treat warnings as errors", does not have any effect.
20917 To disable a specific restriction check, use @code{-RStyle_Checks} gnatcheck
20918 option with the corresponding restriction name as a parameter. @code{-R} is
20919 not available for @code{Style_Checks} and @code{Warnings} options, to disable
20920 warnings and style checks, use the corresponding warning and style options.
20922 @node Project-Wide Checks
20923 @section Project-Wide Checks
20924 @cindex Project-wide checks (for @command{gnatcheck})
20927 In order to perform checks on all units of a given project, you can use
20928 the GNAT driver along with the @option{-P} option:
20930 gnat check -Pproj -rules -from=my_rules
20934 If the project @code{proj} depends upon other projects, you can perform
20935 checks on the project closure using the @option{-U} option:
20937 gnat check -Pproj -U -rules -from=my_rules
20941 Finally, if not all the units are relevant to a particular main
20942 program in the project closure, you can perform checks for the set
20943 of units needed to create a given main program (unit closure) using
20944 the @option{-U} option followed by the name of the main unit:
20946 gnat check -Pproj -U main -rules -from=my_rules
20950 @node Predefined Rules
20951 @section Predefined Rules
20952 @cindex Predefined rules (for @command{gnatcheck})
20955 @c (Jan 2007) Since the global rules are still under development and are not
20956 @c documented, there is no point in explaining the difference between
20957 @c global and local rules
20959 A rule in @command{gnatcheck} is either local or global.
20960 A @emph{local rule} is a rule that applies to a well-defined section
20961 of a program and that can be checked by analyzing only this section.
20962 A @emph{global rule} requires analysis of some global properties of the
20963 whole program (mostly related to the program call graph).
20964 As of @value{NOW}, the implementation of global rules should be
20965 considered to be at a preliminary stage. You can use the
20966 @option{+GLOBAL} option to enable all the global rules, and the
20967 @option{-GLOBAL} rule option to disable all the global rules.
20969 All the global rules in the list below are
20970 so indicated by marking them ``GLOBAL''.
20971 This +GLOBAL and -GLOBAL options are not
20972 included in the list of gnatcheck options above, because at the moment they
20973 are considered as a temporary debug options.
20975 @command{gnatcheck} performs rule checks for generic
20976 instances only for global rules. This limitation may be relaxed in a later
20981 The following subsections document the rules implemented in
20982 @command{gnatcheck}.
20983 The subsection title is the same as the rule identifier, which may be
20984 used as a parameter of the @option{+R} or @option{-R} options.
20988 * Abstract_Type_Declarations::
20989 * Anonymous_Arrays::
20990 * Anonymous_Subtypes::
20992 * Boolean_Relational_Operators::
20994 * Ceiling_Violations::
20996 * Complex_Inlined_Subprograms::
20997 * Controlled_Type_Declarations::
20998 * Declarations_In_Blocks::
20999 * Deep_Inheritance_Hierarchies::
21000 * Deeply_Nested_Generics::
21001 * Deeply_Nested_Inlining::
21003 * Deeply_Nested_Local_Inlining::
21005 * Default_Parameters::
21006 * Direct_Calls_To_Primitives::
21007 * Discriminated_Records::
21008 * Enumeration_Ranges_In_CASE_Statements::
21009 * Exceptions_As_Control_Flow::
21010 * Exits_From_Conditional_Loops::
21011 * EXIT_Statements_With_No_Loop_Name::
21012 * Expanded_Loop_Exit_Names::
21013 * Explicit_Full_Discrete_Ranges::
21014 * Float_Equality_Checks::
21015 * Forbidden_Attributes::
21016 * Forbidden_Pragmas::
21017 * Function_Style_Procedures::
21018 * Generics_In_Subprograms::
21019 * GOTO_Statements::
21020 * Implicit_IN_Mode_Parameters::
21021 * Implicit_SMALL_For_Fixed_Point_Types::
21022 * Improperly_Located_Instantiations::
21023 * Improper_Returns::
21024 * Library_Level_Subprograms::
21027 * Improperly_Called_Protected_Entries::
21030 * Misnamed_Controlling_Parameters::
21031 * Misnamed_Identifiers::
21032 * Multiple_Entries_In_Protected_Definitions::
21034 * Non_Qualified_Aggregates::
21035 * Non_Short_Circuit_Operators::
21036 * Non_SPARK_Attributes::
21037 * Non_Tagged_Derived_Types::
21038 * Non_Visible_Exceptions::
21039 * Numeric_Literals::
21040 * OTHERS_In_Aggregates::
21041 * OTHERS_In_CASE_Statements::
21042 * OTHERS_In_Exception_Handlers::
21043 * Outer_Loop_Exits::
21044 * Overloaded_Operators::
21045 * Overly_Nested_Control_Structures::
21046 * Parameters_Out_Of_Order::
21047 * Positional_Actuals_For_Defaulted_Generic_Parameters::
21048 * Positional_Actuals_For_Defaulted_Parameters::
21049 * Positional_Components::
21050 * Positional_Generic_Parameters::
21051 * Positional_Parameters::
21052 * Predefined_Numeric_Types::
21053 * Raising_External_Exceptions::
21054 * Raising_Predefined_Exceptions::
21055 * Separate_Numeric_Error_Handlers::
21058 * Side_Effect_Functions::
21061 * Too_Many_Parents::
21062 * Unassigned_OUT_Parameters::
21063 * Uncommented_BEGIN_In_Package_Bodies::
21064 * Unconditional_Exits::
21065 * Unconstrained_Array_Returns::
21066 * Universal_Ranges::
21067 * Unnamed_Blocks_And_Loops::
21069 * Unused_Subprograms::
21071 * USE_PACKAGE_Clauses::
21072 * Visible_Components::
21073 * Volatile_Objects_Without_Address_Clauses::
21077 @node Abstract_Type_Declarations
21078 @subsection @code{Abstract_Type_Declarations}
21079 @cindex @code{Abstract_Type_Declarations} rule (for @command{gnatcheck})
21082 Flag all declarations of abstract types. For an abstract private
21083 type, both the private and full type declarations are flagged.
21085 This rule has no parameters.
21088 @node Anonymous_Arrays
21089 @subsection @code{Anonymous_Arrays}
21090 @cindex @code{Anonymous_Arrays} rule (for @command{gnatcheck})
21093 Flag all anonymous array type definitions (by Ada semantics these can only
21094 occur in object declarations).
21096 This rule has no parameters.
21098 @node Anonymous_Subtypes
21099 @subsection @code{Anonymous_Subtypes}
21100 @cindex @code{Anonymous_Subtypes} rule (for @command{gnatcheck})
21103 Flag all uses of anonymous subtypes. A use of an anonymous subtype is
21104 any instance of a subtype indication with a constraint, other than one
21105 that occurs immediately within a subtype declaration. Any use of a range
21106 other than as a constraint used immediately within a subtype declaration
21107 is considered as an anonymous subtype.
21109 An effect of this rule is that @code{for} loops such as the following are
21110 flagged (since @code{1..N} is formally a ``range''):
21112 @smallexample @c ada
21113 for I in 1 .. N loop
21119 Declaring an explicit subtype solves the problem:
21121 @smallexample @c ada
21122 subtype S is Integer range 1..N;
21130 This rule has no parameters.
21133 @subsection @code{Blocks}
21134 @cindex @code{Blocks} rule (for @command{gnatcheck})
21137 Flag each block statement.
21139 This rule has no parameters.
21141 @node Boolean_Relational_Operators
21142 @subsection @code{Boolean_Relational_Operators}
21143 @cindex @code{Boolean_Relational_Operators} rule (for @command{gnatcheck})
21146 Flag each call to a predefined relational operator (``<'', ``>'', ``<='',
21147 ``>='', ``='' and ``/='') for the predefined Boolean type.
21148 (This rule is useful in enforcing the SPARK language restrictions.)
21150 Calls to predefined relational operators of any type derived from
21151 @code{Standard.Boolean} are not detected. Calls to user-defined functions
21152 with these designators, and uses of operators that are renamings
21153 of the predefined relational operators for @code{Standard.Boolean},
21154 are likewise not detected.
21156 This rule has no parameters.
21159 @node Ceiling_Violations
21160 @subsection @code{Ceiling5_Violations} (under construction, GLOBAL)
21161 @cindex @code{Ceiling_Violations} rule (for @command{gnatcheck})
21164 Flag invocations of a protected operation by a task whose priority exceeds
21165 the protected object's ceiling.
21167 As of @value{NOW}, this rule has the following limitations:
21172 We consider only pragmas Priority and Interrupt_Priority as means to define
21173 a task/protected operation priority. We do not consider the effect of using
21174 Ada.Dynamic_Priorities.Set_Priority procedure;
21177 We consider only base task priorities, and no priority inheritance. That is,
21178 we do not make a difference between calls issued during task activation and
21179 execution of the sequence of statements from task body;
21182 Any situation when the priority of protected operation caller is set by a
21183 dynamic expression (that is, the corresponding Priority or
21184 Interrupt_Priority pragma has a non-static expression as an argument) we
21185 treat as a priority inconsistency (and, therefore, detect this situation).
21189 At the moment the notion of the main subprogram is not implemented in
21190 gnatcheck, so any pragma Priority in a library level subprogram body (in case
21191 if this subprogram can be a main subprogram of a partition) changes the
21192 priority of an environment task. So if we have more then one such pragma in
21193 the set of processed sources, the pragma that is processed last, defines the
21194 priority of an environment task.
21196 This rule has no parameters.
21199 @node Controlled_Type_Declarations
21200 @subsection @code{Controlled_Type_Declarations}
21201 @cindex @code{Controlled_Type_Declarations} rule (for @command{gnatcheck})
21204 Flag all declarations of controlled types. A declaration of a private type
21205 is flagged if its full declaration declares a controlled type. A declaration
21206 of a derived type is flagged if its ancestor type is controlled. Subtype
21207 declarations are not checked. A declaration of a type that itself is not a
21208 descendant of a type declared in @code{Ada.Finalization} but has a controlled
21209 component is not checked.
21211 This rule has no parameters.
21214 @node Complex_Inlined_Subprograms
21215 @subsection @code{Complex_Inlined_Subprograms}
21216 @cindex @code{Complex_Inlined_Subprograms} rule (for @command{gnatcheck})
21219 Flags a subprogram (or generic subprogram) if
21220 pragma Inline is applied to the subprogram and at least one of the following
21225 it contains at least one complex declaration such as a subprogram body,
21226 package, task, protected object declaration, or a generic instantiation
21227 (except instantiation of @code{Ada.Unchecked_Conversion});
21230 it contains at least one complex statement such as a loop, a case
21231 or a if statement, or a short circuit control form;
21234 the number of statements exceeds
21235 a value specified by the @option{N} rule parameter;
21239 This rule has the following (mandatory) parameter for the @option{+R} option:
21243 Positive integer specifying the maximum allowed total number of statements
21244 in the subprogram body.
21248 @node Declarations_In_Blocks
21249 @subsection @code{Declarations_In_Blocks}
21250 @cindex @code{Declarations_In_Blocks} rule (for @command{gnatcheck})
21253 Flag all block statements containing local declarations. A @code{declare}
21254 block with an empty @i{declarative_part} or with a @i{declarative part}
21255 containing only pragmas and/or @code{use} clauses is not flagged.
21257 This rule has no parameters.
21260 @node Deep_Inheritance_Hierarchies
21261 @subsection @code{Deep_Inheritance_Hierarchies}
21262 @cindex @code{Deep_Inheritance_Hierarchies} rule (for @command{gnatcheck})
21265 Flags a tagged derived type declaration or an interface type declaration if
21266 its depth (in its inheritance
21267 hierarchy) exceeds the value specified by the @option{N} rule parameter.
21269 The inheritance depth of a tagged type or interface type is defined as 0 for
21270 a type with no parent and no progenitor, and otherwise as 1 + max of the
21271 depths of the immediate parent and immediate progenitors.
21273 This rule does not flag private extension
21274 declarations. In the case of a private extension, the correspondong full
21275 declaration is checked.
21277 This rule has the following (mandatory) parameter for the @option{+R} option:
21281 Integer not less then -1 specifying the maximal allowed depth of any inheritance
21282 hierarchy. If the rule parameter is set to -1, the rule flags all the declarations
21283 of tagged and interface types.
21287 @node Deeply_Nested_Generics
21288 @subsection @code{Deeply_Nested_Generics}
21289 @cindex @code{Deeply_Nested_Generics} rule (for @command{gnatcheck})
21292 Flags a generic declaration nested in another generic declaration if
21293 the nesting level of the inner generic exceeds
21294 a value specified by the @option{N} rule parameter.
21295 The nesting level is the number of generic declaratons that enclose the given
21296 (generic) declaration. Formal packages are not flagged by this rule.
21298 This rule has the following (mandatory) parameters for the @option{+R} option:
21302 Positive integer specifying the maximal allowed nesting level
21303 for a generic declaration.
21306 @node Deeply_Nested_Inlining
21307 @subsection @code{Deeply_Nested_Inlining}
21308 @cindex @code{Deeply_Nested_Inlining} rule (for @command{gnatcheck})
21311 Flags a subprogram (or generic subprogram) if
21312 pragma Inline has been applied to the subprogram but the subprogram
21313 calls to another inlined subprogram that results in nested inlining
21314 with nesting depth exceeding the value specified by the
21315 @option{N} rule parameter.
21317 This rule requires the global analysis of all the compilation units that
21318 are @command{gnatcheck} arguments; such analysis may affect the tool's
21321 This rule has the following (mandatory) parameter for the @option{+R} option:
21325 Positive integer specifying the maximal allowed level of nested inlining.
21330 @node Deeply_Nested_Local_Inlining
21331 @subsection @code{Deeply_Nested_Local_Inlining}
21332 @cindex @code{Deeply_Nested_Local_Inlining} rule (for @command{gnatcheck})
21335 Flags a subprogram body if a pragma @code{Inline} is applied to the
21336 corresponding subprogram (or generic subprogram) and the body contains a call
21337 to another inlined subprogram that results in nested inlining with nesting
21338 depth more then a value specified by the @option{N} rule parameter.
21339 This rule is similar to @code{Deeply_Nested_Inlining} rule, but it
21340 assumes that calls to subprograms in
21341 with'ed units are not inlided, so all the analysis of the depth of inlining is
21342 limited by the compilation unit where the subprogram body is located and the
21343 units it depends semantically upon. Such analysis may be usefull for the case
21344 when neiter @option{-gnatn} nor @option{-gnatN} option is used when building
21347 This rule has the following (mandatory) parameters for the @option{+R} option:
21351 Positive integer specifying the maximal allowed level of nested inlining.
21356 @node Default_Parameters
21357 @subsection @code{Default_Parameters}
21358 @cindex @code{Default_Parameters} rule (for @command{gnatcheck})
21361 Flag all default expressions for subprogram parameters. Parameter
21362 declarations of formal and generic subprograms are also checked.
21364 This rule has no parameters.
21367 @node Direct_Calls_To_Primitives
21368 @subsection @code{Direct_Calls_To_Primitives}
21369 @cindex @code{Direct_Calls_To_Primitives} rule (for @command{gnatcheck})
21372 Flags any non-dispatching call to a dispatching primitive operation, except
21373 for the common idiom where a primitive subprogram for a tagged type
21374 directly calls the same primitive subprogram of the type's immediate ancestor.
21376 This rule has no parameters.
21379 @node Discriminated_Records
21380 @subsection @code{Discriminated_Records}
21381 @cindex @code{Discriminated_Records} rule (for @command{gnatcheck})
21384 Flag all declarations of record types with discriminants. Only the
21385 declarations of record and record extension types are checked. Incomplete,
21386 formal, private, derived and private extension type declarations are not
21387 checked. Task and protected type declarations also are not checked.
21389 This rule has no parameters.
21392 @node Enumeration_Ranges_In_CASE_Statements
21393 @subsection @code{Enumeration_Ranges_In_CASE_Statements}
21394 @cindex @code{Enumeration_Ranges_In_CASE_Statements} (for @command{gnatcheck})
21397 Flag each use of a range of enumeration literals as a choice in a
21398 @code{case} statement.
21399 All forms for specifying a range (explicit ranges
21400 such as @code{A .. B}, subtype marks and @code{'Range} attributes) are flagged.
21401 An enumeration range is
21402 flagged even if contains exactly one enumeration value or no values at all. A
21403 type derived from an enumeration type is considered as an enumeration type.
21405 This rule helps prevent maintenance problems arising from adding an
21406 enumeration value to a type and having it implicitly handled by an existing
21407 @code{case} statement with an enumeration range that includes the new literal.
21409 This rule has no parameters.
21412 @node Exceptions_As_Control_Flow
21413 @subsection @code{Exceptions_As_Control_Flow}
21414 @cindex @code{Exceptions_As_Control_Flow} (for @command{gnatcheck})
21417 Flag each place where an exception is explicitly raised and handled in the
21418 same subprogram body. A @code{raise} statement in an exception handler,
21419 package body, task body or entry body is not flagged.
21421 The rule has no parameters.
21423 @node Exits_From_Conditional_Loops
21424 @subsection @code{Exits_From_Conditional_Loops}
21425 @cindex @code{Exits_From_Conditional_Loops} (for @command{gnatcheck})
21428 Flag any exit statement if it transfers the control out of a @code{for} loop
21429 or a @code{while} loop. This includes cases when the @code{exit} statement
21430 applies to a @code{FOR} or @code{while} loop, and cases when it is enclosed
21431 in some @code{for} or @code{while} loop, but transfers the control from some
21432 outer (inconditional) @code{loop} statement.
21434 The rule has no parameters.
21437 @node EXIT_Statements_With_No_Loop_Name
21438 @subsection @code{EXIT_Statements_With_No_Loop_Name}
21439 @cindex @code{EXIT_Statements_With_No_Loop_Name} (for @command{gnatcheck})
21442 Flag each @code{exit} statement that does not specify the name of the loop
21445 The rule has no parameters.
21448 @node Expanded_Loop_Exit_Names
21449 @subsection @code{Expanded_Loop_Exit_Names}
21450 @cindex @code{Expanded_Loop_Exit_Names} rule (for @command{gnatcheck})
21453 Flag all expanded loop names in @code{exit} statements.
21455 This rule has no parameters.
21457 @node Explicit_Full_Discrete_Ranges
21458 @subsection @code{Explicit_Full_Discrete_Ranges}
21459 @cindex @code{Explicit_Full_Discrete_Ranges} rule (for @command{gnatcheck})
21462 Flag each discrete range that has the form @code{A'First .. A'Last}.
21464 This rule has no parameters.
21466 @node Float_Equality_Checks
21467 @subsection @code{Float_Equality_Checks}
21468 @cindex @code{Float_Equality_Checks} rule (for @command{gnatcheck})
21471 Flag all calls to the predefined equality operations for floating-point types.
21472 Both ``@code{=}'' and ``@code{/=}'' operations are checked.
21473 User-defined equality operations are not flagged, nor are ``@code{=}''
21474 and ``@code{/=}'' operations for fixed-point types.
21476 This rule has no parameters.
21479 @node Forbidden_Attributes
21480 @subsection @code{Forbidden_Attributes}
21481 @cindex @code{Forbidden_Attributes} rule (for @command{gnatcheck})
21484 Flag each use of the specified attributes. The attributes to be detected are
21485 named in the rule's parameters.
21487 This rule has the following parameters:
21490 @item For the @option{+R} option
21493 @item @emph{Attribute_Designator}
21494 Adds the specified attribute to the set of attributes to be detected and sets
21495 the detection checks for all the specified attributes ON.
21496 If @emph{Attribute_Designator}
21497 does not denote any attribute defined in the Ada standard
21499 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference
21500 Manual}, it is treated as the name of unknown attribute.
21503 All the GNAT-specific attributes are detected; this sets
21504 the detection checks for all the specified attributes ON.
21507 All attributes are detected; this sets the rule ON.
21510 @item For the @option{-R} option
21512 @item @emph{Attribute_Designator}
21513 Removes the specified attribute from the set of attributes to be
21514 detected without affecting detection checks for
21515 other attributes. If @emph{Attribute_Designator} does not correspond to any
21516 attribute defined in the Ada standard or in
21517 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference Manual},
21518 this option is treated as turning OFF detection of all unknown attributes.
21521 Turn OFF detection of all GNAT-specific attributes
21524 Clear the list of the attributes to be detected and
21530 Parameters are not case sensitive. If @emph{Attribute_Designator} does not
21531 have the syntax of an Ada identifier and therefore can not be considered as a
21532 (part of an) attribute designator, a diagnostic message is generated and the
21533 corresponding parameter is ignored. (If an attribute allows a static
21534 expression to be a part of the attribute designator, this expression is
21535 ignored by this rule.)
21537 When more then one parameter is given in the same rule option, the parameters
21538 must be separated by commas.
21540 If more then one option for this rule is specified for the gnatcheck call, a
21541 new option overrides the previous one(s).
21543 The @option{+R} option with no parameters turns the rule ON, with the set of
21544 attributes to be detected defined by the previous rule options.
21545 (By default this set is empty, so if the only option specified for the rule is
21546 @option{+RForbidden_Attributes} (with
21547 no parameter), then the rule is enabled, but it does not detect anything).
21548 The @option{-R} option with no parameter turns the rule OFF, but it does not
21549 affect the set of attributes to be detected.
21552 @node Forbidden_Pragmas
21553 @subsection @code{Forbidden_Pragmas}
21554 @cindex @code{Forbidden_Pragmas} rule (for @command{gnatcheck})
21557 Flag each use of the specified pragmas. The pragmas to be detected
21558 are named in the rule's parameters.
21560 This rule has the following parameters:
21563 @item For the @option{+R} option
21566 @item @emph{Pragma_Name}
21567 Adds the specified pragma to the set of pragmas to be
21568 checked and sets the checks for all the specified pragmas
21569 ON. @emph{Pragma_Name} is treated as a name of a pragma. If it
21570 does not correspond to any pragma name defined in the Ada
21571 standard or to the name of a GNAT-specific pragma defined
21572 in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
21573 Manual}, it is treated as the name of unknown pragma.
21576 All the GNAT-specific pragmas are detected; this sets
21577 the checks for all the specified pragmas ON.
21580 All pragmas are detected; this sets the rule ON.
21583 @item For the @option{-R} option
21585 @item @emph{Pragma_Name}
21586 Removes the specified pragma from the set of pragmas to be
21587 checked without affecting checks for
21588 other pragmas. @emph{Pragma_Name} is treated as a name
21589 of a pragma. If it does not correspond to any pragma
21590 defined in the Ada standard or to any name defined in
21591 @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
21592 this option is treated as turning OFF detection of all unknown pragmas.
21595 Turn OFF detection of all GNAT-specific pragmas
21598 Clear the list of the pragmas to be detected and
21604 Parameters are not case sensitive. If @emph{Pragma_Name} does not have
21605 the syntax of an Ada identifier and therefore can not be considered
21606 as a pragma name, a diagnostic message is generated and the corresponding
21607 parameter is ignored.
21609 When more then one parameter is given in the same rule option, the parameters
21610 must be separated by a comma.
21612 If more then one option for this rule is specified for the @command{gnatcheck}
21613 call, a new option overrides the previous one(s).
21615 The @option{+R} option with no parameters turns the rule ON with the set of
21616 pragmas to be detected defined by the previous rule options.
21617 (By default this set is empty, so if the only option specified for the rule is
21618 @option{+RForbidden_Pragmas} (with
21619 no parameter), then the rule is enabled, but it does not detect anything).
21620 The @option{-R} option with no parameter turns the rule OFF, but it does not
21621 affect the set of pragmas to be detected.
21626 @node Function_Style_Procedures
21627 @subsection @code{Function_Style_Procedures}
21628 @cindex @code{Function_Style_Procedures} rule (for @command{gnatcheck})
21631 Flag each procedure that can be rewritten as a function. A procedure can be
21632 converted into a function if it has exactly one parameter of mode @code{out}
21633 and no parameters of mode @code{in out}. Procedure declarations,
21634 formal procedure declarations, and generic procedure declarations are always
21636 bodies and body stubs are flagged only if they do not have corresponding
21637 separate declarations. Procedure renamings and procedure instantiations are
21640 If a procedure can be rewritten as a function, but its @code{out} parameter is
21641 of a limited type, it is not flagged.
21643 Protected procedures are not flagged. Null procedures also are not flagged.
21645 This rule has no parameters.
21648 @node Generics_In_Subprograms
21649 @subsection @code{Generics_In_Subprograms}
21650 @cindex @code{Generics_In_Subprograms} rule (for @command{gnatcheck})
21653 Flag each declaration of a generic unit in a subprogram. Generic
21654 declarations in the bodies of generic subprograms are also flagged.
21655 A generic unit nested in another generic unit is not flagged.
21656 If a generic unit is
21657 declared in a local package that is declared in a subprogram body, the
21658 generic unit is flagged.
21660 This rule has no parameters.
21663 @node GOTO_Statements
21664 @subsection @code{GOTO_Statements}
21665 @cindex @code{GOTO_Statements} rule (for @command{gnatcheck})
21668 Flag each occurrence of a @code{goto} statement.
21670 This rule has no parameters.
21673 @node Implicit_IN_Mode_Parameters
21674 @subsection @code{Implicit_IN_Mode_Parameters}
21675 @cindex @code{Implicit_IN_Mode_Parameters} rule (for @command{gnatcheck})
21678 Flag each occurrence of a formal parameter with an implicit @code{in} mode.
21679 Note that @code{access} parameters, although they technically behave
21680 like @code{in} parameters, are not flagged.
21682 This rule has no parameters.
21685 @node Implicit_SMALL_For_Fixed_Point_Types
21686 @subsection @code{Implicit_SMALL_For_Fixed_Point_Types}
21687 @cindex @code{Implicit_SMALL_For_Fixed_Point_Types} rule (for @command{gnatcheck})
21690 Flag each fixed point type declaration that lacks an explicit
21691 representation clause to define its @code{'Small} value.
21692 Since @code{'Small} can be defined only for ordinary fixed point types,
21693 decimal fixed point type declarations are not checked.
21695 This rule has no parameters.
21698 @node Improperly_Located_Instantiations
21699 @subsection @code{Improperly_Located_Instantiations}
21700 @cindex @code{Improperly_Located_Instantiations} rule (for @command{gnatcheck})
21703 Flag all generic instantiations in library-level package specs
21704 (including library generic packages) and in all subprogram bodies.
21706 Instantiations in task and entry bodies are not flagged. Instantiations in the
21707 bodies of protected subprograms are flagged.
21709 This rule has no parameters.
21713 @node Improper_Returns
21714 @subsection @code{Improper_Returns}
21715 @cindex @code{Improper_Returns} rule (for @command{gnatcheck})
21718 Flag each explicit @code{return} statement in procedures, and
21719 multiple @code{return} statements in functions.
21720 Diagnostic messages are generated for all @code{return} statements
21721 in a procedure (thus each procedure must be written so that it
21722 returns implicitly at the end of its statement part),
21723 and for all @code{return} statements in a function after the first one.
21724 This rule supports the stylistic convention that each subprogram
21725 should have no more than one point of normal return.
21727 This rule has no parameters.
21730 @node Library_Level_Subprograms
21731 @subsection @code{Library_Level_Subprograms}
21732 @cindex @code{Library_Level_Subprograms} rule (for @command{gnatcheck})
21735 Flag all library-level subprograms (including generic subprogram instantiations).
21737 This rule has no parameters.
21740 @node Local_Packages
21741 @subsection @code{Local_Packages}
21742 @cindex @code{Local_Packages} rule (for @command{gnatcheck})
21745 Flag all local packages declared in package and generic package
21747 Local packages in bodies are not flagged.
21749 This rule has no parameters.
21752 @node Improperly_Called_Protected_Entries
21753 @subsection @code{Improperly_Called_Protected_Entries} (under construction, GLOBAL)
21754 @cindex @code{Improperly_Called_Protected_Entries} rule (for @command{gnatcheck})
21757 Flag each protected entry that can be called from more than one task.
21759 This rule has no parameters.
21763 @subsection @code{Metrics}
21764 @cindex @code{Metrics} rule (for @command{gnatcheck})
21767 There is a set of checks based on computing a metric value and comparing the
21768 result with the specified upper (or lower, depending on a specific metric)
21769 value specified for a given metric. A construct is flagged if a given metric
21770 is applicable (can be computed) for it and the computed value is greater
21771 then (lover then) the specified upper (lower) bound.
21773 The name of any metric-based rule consists of the prefix @code{Metrics_}
21774 followed by the name of the corresponding metric (see the table below).
21775 For @option{+R} option, each metric-based rule has a numeric parameter
21776 specifying the bound (integer or real, depending on a metric), @option{-R}
21777 option for metric rules does not have a parameter.
21779 The following table shows the metric names for that the corresponding
21780 metrics-based checks are supported by gnatcheck, including the
21781 constraint that must be satisfied by the bound that is specified for the check
21782 and what bound - upper (U) or lower (L) - should be specified.
21784 @multitable {@code{Cyclomatic_Complexity}}{Cyclomatic complexity}{Positive integer}
21786 @headitem Check Name @tab Description @tab Bounds Value
21789 @item @b{Check Name} @tab @b{Description} @tab @b{Bounds Value}
21791 @c Above conditional code is workaround to bug in texi2html (Feb 2008)
21792 @item @code{Essential_Complexity} @tab Essential complexity @tab Positive integer (U)
21793 @item @code{Cyclomatic_Complexity} @tab Cyclomatic complexity @tab Positive integer (U)
21794 @item @code{LSLOC} @tab Logical Source Lines of Code @tab Positive integer (U)
21798 The meaning and the computed values for all these metrics are exactly
21799 the same as for the corresponding metrics in @command{gnatmetric}.
21801 @emph{Example:} the rule
21803 +RMetrics_Cyclomatic_Complexity : 7
21806 means that all bodies with cyclomatic complexity exceeding 7 will be flagged.
21808 To turn OFF the check for cyclomatic complexity metric, use the following option:
21810 -RMetrics_Cyclomatic_Complexity
21814 @node Misnamed_Controlling_Parameters
21815 @subsection @code{Misnamed_Controlling_Parameters}
21816 @cindex @code{Misnamed_Controlling_Parameters} rule (for @command{gnatcheck})
21819 Flags a declaration of a dispatching operation, if the first parameter is
21820 not a controlling one and its name is not @code{This} (the check for
21821 parameter name is not case-sensitive). Declarations of dispatching functions
21822 with controlling result and no controlling parameter are never flagged.
21824 A subprogram body declaration, subprogram renaming declaration or subprogram
21825 body stub is flagged only if it is not a completion of a prior subprogram
21828 This rule has no parameters.
21832 @node Misnamed_Identifiers
21833 @subsection @code{Misnamed_Identifiers}
21834 @cindex @code{Misnamed_Identifiers} rule (for @command{gnatcheck})
21837 Flag the declaration of each identifier that does not have a suffix
21838 corresponding to the kind of entity being declared.
21839 The following declarations are checked:
21846 subtype declarations
21849 constant declarations (but not number declarations)
21852 package renaming declarations (but not generic package renaming
21857 This rule may have parameters. When used without parameters, the rule enforces
21858 the following checks:
21862 type-defining names end with @code{_T}, unless the type is an access type,
21863 in which case the suffix must be @code{_A}
21865 constant names end with @code{_C}
21867 names defining package renamings end with @code{_R}
21871 Defining identifiers from incomplete type declarations are never flagged.
21873 For a private type declaration (including private extensions), the defining
21874 identifier from the private type declaration is checked against the type
21875 suffix (even if the corresponding full declaration is an access type
21876 declaration), and the defining identifier from the corresponding full type
21877 declaration is not checked.
21880 For a deferred constant, the defining name in the corresponding full constant
21881 declaration is not checked.
21883 Defining names of formal types are not checked.
21885 The rule may have the following parameters:
21889 For the @option{+R} option:
21892 Sets the default listed above for all the names to be checked.
21894 @item Type_Suffix=@emph{string}
21895 Specifies the suffix for a type name.
21897 @item Access_Suffix=@emph{string}
21898 Specifies the suffix for an access type name. If
21899 this parameter is set, it overrides for access
21900 types the suffix set by the @code{Type_Suffix} parameter.
21901 For access types, @emph{string} may have the following format:
21902 @emph{suffix1(suffix2)}. That means that an access type name
21903 should have the @emph{suffix1} suffix except for the case when
21904 the designated type is also an access type, in this case the
21905 type name should have the @emph{suffix1 & suffix2} suffix.
21907 @item Class_Access_Suffix=@emph{string}
21908 Specifies the suffix for the name of an access type that points to some class-wide
21909 type. If this parameter is set, it overrides for such access
21910 types the suffix set by the @code{Type_Suffix} or @code{Access_Suffix}
21913 @item Class_Subtype_Suffix=@emph{string}
21914 Specifies the suffix for the name of a subtype that denotes a class-wide type.
21916 @item Constant_Suffix=@emph{string}
21917 Specifies the suffix for a constant name.
21919 @item Renaming_Suffix=@emph{string}
21920 Specifies the suffix for a package renaming name.
21924 For the @option{-R} option:
21927 Remove all the suffixes specified for the
21928 identifier suffix checks, whether by default or
21929 as specified by other rule parameters. All the
21930 checks for this rule are disabled as a result.
21933 Removes the suffix specified for types. This
21934 disables checks for types but does not disable
21935 any other checks for this rule (including the
21936 check for access type names if @code{Access_Suffix} is
21939 @item Access_Suffix
21940 Removes the suffix specified for access types.
21941 This disables checks for access type names but
21942 does not disable any other checks for this rule.
21943 If @code{Type_Suffix} is set, access type names are
21944 checked as ordinary type names.
21946 @item Class_Access_Suffix
21947 Removes the suffix specified for access types pointing to class-wide
21948 type. This disables specific checks for names of access types pointing to
21949 class-wide types but does not disable any other checks for this rule.
21950 If @code{Type_Suffix} is set, access type names are
21951 checked as ordinary type names. If @code{Access_Suffix} is set, these
21952 access types are checked as any other access type name.
21954 @item Class_Subtype_Suffix=@emph{string}
21955 Removes the suffix specified for subtype names.
21956 This disables checks for subtype names but
21957 does not disable any other checks for this rule.
21959 @item Constant_Suffix
21960 Removes the suffix specified for constants. This
21961 disables checks for constant names but does not
21962 disable any other checks for this rule.
21964 @item Renaming_Suffix
21965 Removes the suffix specified for package
21966 renamings. This disables checks for package
21967 renamings but does not disable any other checks
21973 If more than one parameter is used, parameters must be separated by commas.
21975 If more than one option is specified for the @command{gnatcheck} invocation,
21976 a new option overrides the previous one(s).
21978 The @option{+RMisnamed_Identifiers} option (with no parameter) enables
21980 name suffixes specified by previous options used for this rule.
21982 The @option{-RMisnamed_Identifiers} option (with no parameter) disables
21983 all the checks but keeps
21984 all the suffixes specified by previous options used for this rule.
21986 The @emph{string} value must be a valid suffix for an Ada identifier (after
21987 trimming all the leading and trailing space characters, if any).
21988 Parameters are not case sensitive, except the @emph{string} part.
21990 If any error is detected in a rule parameter, the parameter is ignored.
21991 In such a case the options that are set for the rule are not
21996 @node Multiple_Entries_In_Protected_Definitions
21997 @subsection @code{Multiple_Entries_In_Protected_Definitions}
21998 @cindex @code{Multiple_Entries_In_Protected_Definitions} rule (for @command{gnatcheck})
22001 Flag each protected definition (i.e., each protected object/type declaration)
22002 that defines more than one entry.
22003 Diagnostic messages are generated for all the entry declarations
22004 except the first one. An entry family is counted as one entry. Entries from
22005 the private part of the protected definition are also checked.
22007 This rule has no parameters.
22010 @subsection @code{Name_Clashes}
22011 @cindex @code{Name_Clashes} rule (for @command{gnatcheck})
22014 Check that certain names are not used as defining identifiers. To activate
22015 this rule, you need to supply a reference to the dictionary file(s) as a rule
22016 parameter(s) (more then one dictionary file can be specified). If no
22017 dictionary file is set, this rule will not cause anything to be flagged.
22018 Only defining occurrences, not references, are checked.
22019 The check is not case-sensitive.
22021 This rule is enabled by default, but without setting any corresponding
22022 dictionary file(s); thus the default effect is to do no checks.
22024 A dictionary file is a plain text file. The maximum line length for this file
22025 is 1024 characters. If the line is longer then this limit, extra characters
22028 Each line can be either an empty line, a comment line, or a line containing
22029 a list of identifiers separated by space or HT characters.
22030 A comment is an Ada-style comment (from @code{--} to end-of-line).
22031 Identifiers must follow the Ada syntax for identifiers.
22032 A line containing one or more identifiers may end with a comment.
22034 @node Non_Qualified_Aggregates
22035 @subsection @code{Non_Qualified_Aggregates}
22036 @cindex @code{Non_Qualified_Aggregates} rule (for @command{gnatcheck})
22039 Flag each non-qualified aggregate.
22040 A non-qualified aggregate is an
22041 aggregate that is not the expression of a qualified expression. A
22042 string literal is not considered an aggregate, but an array
22043 aggregate of a string type is considered as a normal aggregate.
22044 Aggregates of anonymous array types are not flagged.
22046 This rule has no parameters.
22049 @node Non_Short_Circuit_Operators
22050 @subsection @code{Non_Short_Circuit_Operators}
22051 @cindex @code{Non_Short_Circuit_Operators} rule (for @command{gnatcheck})
22054 Flag all calls to predefined @code{and} and @code{or} operators for
22055 any boolean type. Calls to
22056 user-defined @code{and} and @code{or} and to operators defined by renaming
22057 declarations are not flagged. Calls to predefined @code{and} and @code{or}
22058 operators for modular types or boolean array types are not flagged.
22060 This rule has no parameters.
22064 @node Non_SPARK_Attributes
22065 @subsection @code{Non_SPARK_Attributes}
22066 @cindex @code{Non_SPARK_Attributes} rule (for @command{gnatcheck})
22069 The SPARK language defines the following subset of Ada 95 attribute
22070 designators as those that can be used in SPARK programs. The use of
22071 any other attribute is flagged.
22074 @item @code{'Adjacent}
22077 @item @code{'Ceiling}
22078 @item @code{'Component_Size}
22079 @item @code{'Compose}
22080 @item @code{'Copy_Sign}
22081 @item @code{'Delta}
22082 @item @code{'Denorm}
22083 @item @code{'Digits}
22084 @item @code{'Exponent}
22085 @item @code{'First}
22086 @item @code{'Floor}
22088 @item @code{'Fraction}
22090 @item @code{'Leading_Part}
22091 @item @code{'Length}
22092 @item @code{'Machine}
22093 @item @code{'Machine_Emax}
22094 @item @code{'Machine_Emin}
22095 @item @code{'Machine_Mantissa}
22096 @item @code{'Machine_Overflows}
22097 @item @code{'Machine_Radix}
22098 @item @code{'Machine_Rounds}
22101 @item @code{'Model}
22102 @item @code{'Model_Emin}
22103 @item @code{'Model_Epsilon}
22104 @item @code{'Model_Mantissa}
22105 @item @code{'Model_Small}
22106 @item @code{'Modulus}
22109 @item @code{'Range}
22110 @item @code{'Remainder}
22111 @item @code{'Rounding}
22112 @item @code{'Safe_First}
22113 @item @code{'Safe_Last}
22114 @item @code{'Scaling}
22115 @item @code{'Signed_Zeros}
22117 @item @code{'Small}
22119 @item @code{'Truncation}
22120 @item @code{'Unbiased_Rounding}
22122 @item @code{'Valid}
22126 This rule has no parameters.
22129 @node Non_Tagged_Derived_Types
22130 @subsection @code{Non_Tagged_Derived_Types}
22131 @cindex @code{Non_Tagged_Derived_Types} rule (for @command{gnatcheck})
22134 Flag all derived type declarations that do not have a record extension part.
22136 This rule has no parameters.
22140 @node Non_Visible_Exceptions
22141 @subsection @code{Non_Visible_Exceptions}
22142 @cindex @code{Non_Visible_Exceptions} rule (for @command{gnatcheck})
22145 Flag constructs leading to the possibility of propagating an exception
22146 out of the scope in which the exception is declared.
22147 Two cases are detected:
22151 An exception declaration in a subprogram body, task body or block
22152 statement is flagged if the body or statement does not contain a handler for
22153 that exception or a handler with an @code{others} choice.
22156 A @code{raise} statement in an exception handler of a subprogram body,
22157 task body or block statement is flagged if it (re)raises a locally
22158 declared exception. This may occur under the following circumstances:
22161 it explicitly raises a locally declared exception, or
22163 it does not specify an exception name (i.e., it is simply @code{raise;})
22164 and the enclosing handler contains a locally declared exception in its
22170 Renamings of local exceptions are not flagged.
22172 This rule has no parameters.
22175 @node Numeric_Literals
22176 @subsection @code{Numeric_Literals}
22177 @cindex @code{Numeric_Literals} rule (for @command{gnatcheck})
22180 Flag each use of a numeric literal in an index expression, and in any
22181 circumstance except for the following:
22185 a literal occurring in the initialization expression for a constant
22186 declaration or a named number declaration, or
22189 an integer literal that is less than or equal to a value
22190 specified by the @option{N} rule parameter.
22194 This rule may have the following parameters for the @option{+R} option:
22198 @emph{N} is an integer literal used as the maximal value that is not flagged
22199 (i.e., integer literals not exceeding this value are allowed)
22202 All integer literals are flagged
22206 If no parameters are set, the maximum unflagged value is 1.
22208 The last specified check limit (or the fact that there is no limit at
22209 all) is used when multiple @option{+R} options appear.
22211 The @option{-R} option for this rule has no parameters.
22212 It disables the rule but retains the last specified maximum unflagged value.
22213 If the @option{+R} option subsequently appears, this value is used as the
22214 threshold for the check.
22217 @node OTHERS_In_Aggregates
22218 @subsection @code{OTHERS_In_Aggregates}
22219 @cindex @code{OTHERS_In_Aggregates} rule (for @command{gnatcheck})
22222 Flag each use of an @code{others} choice in extension aggregates.
22223 In record and array aggregates, an @code{others} choice is flagged unless
22224 it is used to refer to all components, or to all but one component.
22226 If, in case of a named array aggregate, there are two associations, one
22227 with an @code{others} choice and another with a discrete range, the
22228 @code{others} choice is flagged even if the discrete range specifies
22229 exactly one component; for example, @code{(1..1 => 0, others => 1)}.
22231 This rule has no parameters.
22233 @node OTHERS_In_CASE_Statements
22234 @subsection @code{OTHERS_In_CASE_Statements}
22235 @cindex @code{OTHERS_In_CASE_Statements} rule (for @command{gnatcheck})
22238 Flag any use of an @code{others} choice in a @code{case} statement.
22240 This rule has no parameters.
22242 @node OTHERS_In_Exception_Handlers
22243 @subsection @code{OTHERS_In_Exception_Handlers}
22244 @cindex @code{OTHERS_In_Exception_Handlers} rule (for @command{gnatcheck})
22247 Flag any use of an @code{others} choice in an exception handler.
22249 This rule has no parameters.
22252 @node Outer_Loop_Exits
22253 @subsection @code{Outer_Loop_Exits}
22254 @cindex @code{Outer_Loop_Exits} rule (for @command{gnatcheck})
22257 Flag each @code{exit} statement containing a loop name that is not the name
22258 of the immediately enclosing @code{loop} statement.
22260 This rule has no parameters.
22263 @node Overloaded_Operators
22264 @subsection @code{Overloaded_Operators}
22265 @cindex @code{Overloaded_Operators} rule (for @command{gnatcheck})
22268 Flag each function declaration that overloads an operator symbol.
22269 A function body is checked only if the body does not have a
22270 separate spec. Formal functions are also checked. For a
22271 renaming declaration, only renaming-as-declaration is checked
22273 This rule has no parameters.
22276 @node Overly_Nested_Control_Structures
22277 @subsection @code{Overly_Nested_Control_Structures}
22278 @cindex @code{Overly_Nested_Control_Structures} rule (for @command{gnatcheck})
22281 Flag each control structure whose nesting level exceeds the value provided
22282 in the rule parameter.
22284 The control structures checked are the following:
22287 @item @code{if} statement
22288 @item @code{case} statement
22289 @item @code{loop} statement
22290 @item Selective accept statement
22291 @item Timed entry call statement
22292 @item Conditional entry call
22293 @item Asynchronous select statement
22297 The rule has the following parameter for the @option{+R} option:
22301 Positive integer specifying the maximal control structure nesting
22302 level that is not flagged
22306 If the parameter for the @option{+R} option is not specified or
22307 if it is not a positive integer, @option{+R} option is ignored.
22309 If more then one option is specified for the gnatcheck call, the later option and
22310 new parameter override the previous one(s).
22313 @node Parameters_Out_Of_Order
22314 @subsection @code{Parameters_Out_Of_Order}
22315 @cindex @code{Parameters_Out_Of_Order} rule (for @command{gnatcheck})
22318 Flag each subprogram and entry declaration whose formal parameters are not
22319 ordered according to the following scheme:
22323 @item @code{in} and @code{access} parameters first,
22324 then @code{in out} parameters,
22325 and then @code{out} parameters;
22327 @item for @code{in} mode, parameters with default initialization expressions
22332 Only the first violation of the described order is flagged.
22334 The following constructs are checked:
22337 @item subprogram declarations (including null procedures);
22338 @item generic subprogram declarations;
22339 @item formal subprogram declarations;
22340 @item entry declarations;
22341 @item subprogram bodies and subprogram body stubs that do not
22342 have separate specifications
22346 Subprogram renamings are not checked.
22348 This rule has no parameters.
22351 @node Positional_Actuals_For_Defaulted_Generic_Parameters
22352 @subsection @code{Positional_Actuals_For_Defaulted_Generic_Parameters}
22353 @cindex @code{Positional_Actuals_For_Defaulted_Generic_Parameters} rule (for @command{gnatcheck})
22356 Flag each generic actual parameter corresponding to a generic formal
22357 parameter with a default initialization, if positional notation is used.
22359 This rule has no parameters.
22361 @node Positional_Actuals_For_Defaulted_Parameters
22362 @subsection @code{Positional_Actuals_For_Defaulted_Parameters}
22363 @cindex @code{Positional_Actuals_For_Defaulted_Parameters} rule (for @command{gnatcheck})
22366 Flag each actual parameter to a subprogram or entry call where the
22367 corresponding formal parameter has a default expression, if positional
22370 This rule has no parameters.
22372 @node Positional_Components
22373 @subsection @code{Positional_Components}
22374 @cindex @code{Positional_Components} rule (for @command{gnatcheck})
22377 Flag each array, record and extension aggregate that includes positional
22380 This rule has no parameters.
22383 @node Positional_Generic_Parameters
22384 @subsection @code{Positional_Generic_Parameters}
22385 @cindex @code{Positional_Generic_Parameters} rule (for @command{gnatcheck})
22388 Flag each instantiation using positional parameter notation.
22390 This rule has no parameters.
22393 @node Positional_Parameters
22394 @subsection @code{Positional_Parameters}
22395 @cindex @code{Positional_Parameters} rule (for @command{gnatcheck})
22398 Flag each subprogram or entry call using positional parameter notation,
22399 except for the following:
22403 Invocations of prefix or infix operators are not flagged
22405 If the called subprogram or entry has only one formal parameter,
22406 the call is not flagged;
22408 If a subprogram call uses the @emph{Object.Operation} notation, then
22411 the first parameter (that is, @emph{Object}) is not flagged;
22413 if the called subprogram has only two parameters, the second parameter
22414 of the call is not flagged;
22419 This rule has no parameters.
22424 @node Predefined_Numeric_Types
22425 @subsection @code{Predefined_Numeric_Types}
22426 @cindex @code{Predefined_Numeric_Types} rule (for @command{gnatcheck})
22429 Flag each explicit use of the name of any numeric type or subtype defined
22430 in package @code{Standard}.
22432 The rationale for this rule is to detect when the
22433 program may depend on platform-specific characteristics of the implementation
22434 of the predefined numeric types. Note that this rule is over-pessimistic;
22435 for example, a program that uses @code{String} indexing
22436 likely needs a variable of type @code{Integer}.
22437 Another example is the flagging of predefined numeric types with explicit
22440 @smallexample @c ada
22441 subtype My_Integer is Integer range Left .. Right;
22442 Vy_Var : My_Integer;
22446 This rule detects only numeric types and subtypes defined in
22447 @code{Standard}. The use of numeric types and subtypes defined in other
22448 predefined packages (such as @code{System.Any_Priority} or
22449 @code{Ada.Text_IO.Count}) is not flagged
22451 This rule has no parameters.
22455 @node Raising_External_Exceptions
22456 @subsection @code{Raising_External_Exceptions}
22457 @cindex @code{Raising_External_Exceptions} rule (for @command{gnatcheck})
22460 Flag any @code{raise} statement, in a program unit declared in a library
22461 package or in a generic library package, for an exception that is
22462 neither a predefined exception nor an exception that is also declared (or
22463 renamed) in the visible part of the package.
22465 This rule has no parameters.
22469 @node Raising_Predefined_Exceptions
22470 @subsection @code{Raising_Predefined_Exceptions}
22471 @cindex @code{Raising_Predefined_Exceptions} rule (for @command{gnatcheck})
22474 Flag each @code{raise} statement that raises a predefined exception
22475 (i.e., one of the exceptions @code{Constraint_Error}, @code{Numeric_Error},
22476 @code{Program_Error}, @code{Storage_Error}, or @code{Tasking_Error}).
22478 This rule has no parameters.
22480 @node Separate_Numeric_Error_Handlers
22481 @subsection @code{Separate_Numeric_Error_Handlers}
22482 @cindex @code{Separate_Numeric_Error_Handlers} rule (for @command{gnatcheck})
22485 Flags each exception handler that contains a choice for
22486 the predefined @code{Constraint_Error} exception, but does not contain
22487 the choice for the predefined @code{Numeric_Error} exception, or
22488 that contains the choice for @code{Numeric_Error}, but does not contain the
22489 choice for @code{Constraint_Error}.
22491 This rule has no parameters.
22495 @subsection @code{Recursion} (under construction, GLOBAL)
22496 @cindex @code{Recursion} rule (for @command{gnatcheck})
22499 Flag recursive subprograms (cycles in the call graph). Declarations, and not
22500 calls, of recursive subprograms are detected.
22502 This rule has no parameters.
22506 @node Side_Effect_Functions
22507 @subsection @code{Side_Effect_Functions} (under construction, GLOBAL)
22508 @cindex @code{Side_Effect_Functions} rule (for @command{gnatcheck})
22511 Flag functions with side effects.
22513 We define a side effect as changing any data object that is not local for the
22514 body of this function.
22516 At the moment, we do NOT consider a side effect any input-output operations
22517 (changing a state or a content of any file).
22519 We do not consider protected functions for this rule (???)
22521 There are the following sources of side effect:
22524 @item Explicit (or direct) side-effect:
22528 direct assignment to a non-local variable;
22531 direct call to an entity that is known to change some data object that is
22532 not local for the body of this function (Note, that if F1 calls F2 and F2
22533 does have a side effect, this does not automatically mean that F1 also
22534 have a side effect, because it may be the case that F2 is declared in
22535 F1's body and it changes some data object that is global for F2, but
22539 @item Indirect side-effect:
22542 Subprogram calls implicitly issued by:
22545 computing initialization expressions from type declarations as a part
22546 of object elaboration or allocator evaluation;
22548 computing implicit parameters of subprogram or entry calls or generic
22553 activation of a task that change some non-local data object (directly or
22557 elaboration code of a package that is a result of a package instantiation;
22560 controlled objects;
22563 @item Situations when we can suspect a side-effect, but the full static check
22564 is either impossible or too hard:
22567 assignment to access variables or to the objects pointed by access
22571 call to a subprogram pointed by access-to-subprogram value
22579 This rule has no parameters.
22583 @subsection @code{Slices}
22584 @cindex @code{Slices} rule (for @command{gnatcheck})
22587 Flag all uses of array slicing
22589 This rule has no parameters.
22592 @node Too_Many_Parents
22593 @subsection @code{Too_Many_Parents}
22594 @cindex @code{Too_Many_Parents} rule (for @command{gnatcheck})
22597 Flags any type declaration, single task declaration or single protected
22598 declaration that has more then @option{N} parents, @option{N} is a parameter
22600 A parent here is either a (sub)type denoted by the subtype mark from the
22601 parent_subtype_indication (in case of a derived type declaration), or
22602 any of the progenitors from the interface list, if any.
22604 This rule has the following (mandatory) parameters for the @option{+R} option:
22608 Positive integer specifying the maximal allowed number of parents.
22612 @node Unassigned_OUT_Parameters
22613 @subsection @code{Unassigned_OUT_Parameters}
22614 @cindex @code{Unassigned_OUT_Parameters} rule (for @command{gnatcheck})
22617 Flags procedures' @code{out} parameters that are not assigned, and
22618 identifies the contexts in which the assignments are missing.
22620 An @code{out} parameter is flagged in the statements in the procedure
22621 body's handled sequence of statements (before the procedure body's
22622 @code{exception} part, if any) if this sequence of statements contains
22623 no assignments to the parameter.
22625 An @code{out} parameter is flagged in an exception handler in the exception
22626 part of the procedure body's handled sequence of statements if the handler
22627 contains no assignment to the parameter.
22629 Bodies of generic procedures are also considered.
22631 The following are treated as assignments to an @code{out} parameter:
22635 an assignment statement, with the parameter or some component as the target;
22638 passing the parameter (or one of its components) as an @code{out} or
22639 @code{in out} parameter.
22643 This rule does not have any parameters.
22647 @node Uncommented_BEGIN_In_Package_Bodies
22648 @subsection @code{Uncommented_BEGIN_In_Package_Bodies}
22649 @cindex @code{Uncommented_BEGIN_In_Package_Bodies} rule (for @command{gnatcheck})
22652 Flags each package body with declarations and a statement part that does not
22653 include a trailing comment on the line containing the @code{begin} keyword;
22654 this trailing comment needs to specify the package name and nothing else.
22655 The @code{begin} is not flagged if the package body does not
22656 contain any declarations.
22658 If the @code{begin} keyword is placed on the
22659 same line as the last declaration or the first statement, it is flagged
22660 independently of whether the line contains a trailing comment. The
22661 diagnostic message is attached to the line containing the first statement.
22663 This rule has no parameters.
22665 @node Unconditional_Exits
22666 @subsection @code{Unconditional_Exits}
22667 @cindex @code{Unconditional_Exits} rule (for @command{gnatcheck})
22670 Flag unconditional @code{exit} statements.
22672 This rule has no parameters.
22674 @node Unconstrained_Array_Returns
22675 @subsection @code{Unconstrained_Array_Returns}
22676 @cindex @code{Unconstrained_Array_Returns} rule (for @command{gnatcheck})
22679 Flag each function returning an unconstrained array. Function declarations,
22680 function bodies (and body stubs) having no separate specifications,
22681 and generic function instantiations are checked.
22682 Function calls and function renamings are
22685 Generic function declarations, and function declarations in generic
22686 packages are not checked, instead this rule checks the results of
22687 generic instantiations (that is, expanded specification and expanded
22688 body corresponding to an instantiation).
22690 This rule has no parameters.
22692 @node Universal_Ranges
22693 @subsection @code{Universal_Ranges}
22694 @cindex @code{Universal_Ranges} rule (for @command{gnatcheck})
22697 Flag discrete ranges that are a part of an index constraint, constrained
22698 array definition, or @code{for}-loop parameter specification, and whose bounds
22699 are both of type @i{universal_integer}. Ranges that have at least one
22700 bound of a specific type (such as @code{1 .. N}, where @code{N} is a variable
22701 or an expression of non-universal type) are not flagged.
22703 This rule has no parameters.
22706 @node Unnamed_Blocks_And_Loops
22707 @subsection @code{Unnamed_Blocks_And_Loops}
22708 @cindex @code{Unnamed_Blocks_And_Loops} rule (for @command{gnatcheck})
22711 Flag each unnamed block statement and loop statement.
22713 The rule has no parameters.
22718 @node Unused_Subprograms
22719 @subsection @code{Unused_Subprograms} (under construction, GLOBAL)
22720 @cindex @code{Unused_Subprograms} rule (for @command{gnatcheck})
22723 Flag all unused subprograms.
22725 This rule has no parameters.
22731 @node USE_PACKAGE_Clauses
22732 @subsection @code{USE_PACKAGE_Clauses}
22733 @cindex @code{USE_PACKAGE_Clauses} rule (for @command{gnatcheck})
22736 Flag all @code{use} clauses for packages; @code{use type} clauses are
22739 This rule has no parameters.
22742 @node Visible_Components
22743 @subsection @code{Visible_Components}
22744 @cindex @code{Visible_Components} rule (for @command{gnatcheck})
22747 Flags all the type declarations located in the visible part of a library
22748 package or a library generic package that can declare a visible component. A
22749 type is considered as declaring a visible component if it contains a record
22750 definition by its own or as a part of a record extension. Type declaration is
22751 flagged even if it contains a record definition that defines no components.
22753 Declarations located in private parts of local (generic) packages are not
22754 flagged. Declarations in private packages are not flagged.
22756 This rule has no parameters.
22759 @node Volatile_Objects_Without_Address_Clauses
22760 @subsection @code{Volatile_Objects_Without_Address_Clauses}
22761 @cindex @code{Volatile_Objects_Without_Address_Clauses} rule (for @command{gnatcheck})
22764 Flag each volatile object that does not have an address clause.
22766 The following check is made: if the pragma @code{Volatile} is applied to a
22767 data object or to its type, then an address clause must
22768 be supplied for this object.
22770 This rule does not check the components of data objects,
22771 array components that are volatile as a result of the pragma
22772 @code{Volatile_Components}, or objects that are volatile because
22773 they are atomic as a result of pragmas @code{Atomic} or
22774 @code{Atomic_Components}.
22776 Only variable declarations, and not constant declarations, are checked.
22778 This rule has no parameters.
22781 @c *********************************
22782 @node Creating Sample Bodies Using gnatstub
22783 @chapter Creating Sample Bodies Using @command{gnatstub}
22787 @command{gnatstub} creates body stubs, that is, empty but compilable bodies
22788 for library unit declarations.
22790 Note: to invoke @code{gnatstub} with a project file, use the @code{gnat}
22791 driver (see @ref{The GNAT Driver and Project Files}).
22793 To create a body stub, @command{gnatstub} has to compile the library
22794 unit declaration. Therefore, bodies can be created only for legal
22795 library units. Moreover, if a library unit depends semantically upon
22796 units located outside the current directory, you have to provide
22797 the source search path when calling @command{gnatstub}, see the description
22798 of @command{gnatstub} switches below.
22800 By default, all the program unit body stubs generated by @code{gnatstub}
22801 raise the predefined @code{Program_Error} exception, which will catch
22802 accidental calls of generated stubs. This behavior can be changed with
22803 option @option{^--no-exception^/NO_EXCEPTION^} (see below).
22806 * Running gnatstub::
22807 * Switches for gnatstub::
22810 @node Running gnatstub
22811 @section Running @command{gnatstub}
22814 @command{gnatstub} has the command-line interface of the form
22817 $ gnatstub @ovar{switches} @var{filename} @ovar{directory}
22824 is the name of the source file that contains a library unit declaration
22825 for which a body must be created. The file name may contain the path
22827 The file name does not have to follow the GNAT file name conventions. If the
22829 does not follow GNAT file naming conventions, the name of the body file must
22831 explicitly as the value of the @option{^-o^/BODY=^@var{body-name}} option.
22832 If the file name follows the GNAT file naming
22833 conventions and the name of the body file is not provided,
22836 of the body file from the argument file name by replacing the @file{.ads}
22838 with the @file{.adb} suffix.
22841 indicates the directory in which the body stub is to be placed (the default
22846 is an optional sequence of switches as described in the next section
22849 @node Switches for gnatstub
22850 @section Switches for @command{gnatstub}
22856 @cindex @option{^-f^/FULL^} (@command{gnatstub})
22857 If the destination directory already contains a file with the name of the
22859 for the argument spec file, replace it with the generated body stub.
22861 @item ^-hs^/HEADER=SPEC^
22862 @cindex @option{^-hs^/HEADER=SPEC^} (@command{gnatstub})
22863 Put the comment header (i.e., all the comments preceding the
22864 compilation unit) from the source of the library unit declaration
22865 into the body stub.
22867 @item ^-hg^/HEADER=GENERAL^
22868 @cindex @option{^-hg^/HEADER=GENERAL^} (@command{gnatstub})
22869 Put a sample comment header into the body stub.
22871 @item ^--header-file=@var{filename}^/FROM_HEADER_FILE=@var{filename}^
22872 @cindex @option{^--header-file^/FROM_HEADER_FILE=^} (@command{gnatstub})
22873 Use the content of the file as the comment header for a generated body stub.
22877 @cindex @option{-IDIR} (@command{gnatstub})
22879 @cindex @option{-I-} (@command{gnatstub})
22882 @item /NOCURRENT_DIRECTORY
22883 @cindex @option{/NOCURRENT_DIRECTORY} (@command{gnatstub})
22885 ^These switches have ^This switch has^ the same meaning as in calls to
22887 ^They define ^It defines ^ the source search path in the call to
22888 @command{gcc} issued
22889 by @command{gnatstub} to compile an argument source file.
22891 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE=^@var{PATH}
22892 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@command{gnatstub})
22893 This switch has the same meaning as in calls to @command{gcc}.
22894 It defines the additional configuration file to be passed to the call to
22895 @command{gcc} issued
22896 by @command{gnatstub} to compile an argument source file.
22898 @item ^-gnatyM^/MAX_LINE_LENGTH=^@var{n}
22899 @cindex @option{^-gnatyM^/MAX_LINE_LENGTH^} (@command{gnatstub})
22900 (@var{n} is a non-negative integer). Set the maximum line length in the
22901 body stub to @var{n}; the default is 79. The maximum value that can be
22902 specified is 32767. Note that in the special case of configuration
22903 pragma files, the maximum is always 32767 regardless of whether or
22904 not this switch appears.
22906 @item ^-gnaty^/STYLE_CHECKS=^@var{n}
22907 @cindex @option{^-gnaty^/STYLE_CHECKS=^} (@command{gnatstub})
22908 (@var{n} is a non-negative integer from 1 to 9). Set the indentation level in
22909 the generated body sample to @var{n}.
22910 The default indentation is 3.
22912 @item ^-gnatyo^/ORDERED_SUBPROGRAMS^
22913 @cindex @option{^-gnato^/ORDERED_SUBPROGRAMS^} (@command{gnatstub})
22914 Order local bodies alphabetically. (By default local bodies are ordered
22915 in the same way as the corresponding local specs in the argument spec file.)
22917 @item ^-i^/INDENTATION=^@var{n}
22918 @cindex @option{^-i^/INDENTATION^} (@command{gnatstub})
22919 Same as @option{^-gnaty^/STYLE_CHECKS=^@var{n}}
22921 @item ^-k^/TREE_FILE=SAVE^
22922 @cindex @option{^-k^/TREE_FILE=SAVE^} (@command{gnatstub})
22923 Do not remove the tree file (i.e., the snapshot of the compiler internal
22924 structures used by @command{gnatstub}) after creating the body stub.
22926 @item ^-l^/LINE_LENGTH=^@var{n}
22927 @cindex @option{^-l^/LINE_LENGTH^} (@command{gnatstub})
22928 Same as @option{^-gnatyM^/MAX_LINE_LENGTH=^@var{n}}
22930 @item ^--no-exception^/NO_EXCEPTION^
22931 @cindex @option{^--no-exception^/NO_EXCEPTION^} (@command{gnatstub})
22932 Avoind raising PROGRAM_ERROR in the generated bodies of program unit stubs.
22933 This is not always possible for function stubs.
22935 @item ^--no-local-header^/NO_LOCAL_HEADER^
22936 @cindex @option{^--no-local-header^/NO_LOCAL_HEADER^} (@command{gnatstub})
22937 Do not place local comment header with unit name before body stub for a
22940 @item ^-o ^/BODY=^@var{body-name}
22941 @cindex @option{^-o^/BODY^} (@command{gnatstub})
22942 Body file name. This should be set if the argument file name does not
22944 the GNAT file naming
22945 conventions. If this switch is omitted the default name for the body will be
22947 from the argument file name according to the GNAT file naming conventions.
22950 @cindex @option{^-q^/QUIET^} (@command{gnatstub})
22951 Quiet mode: do not generate a confirmation when a body is
22952 successfully created, and do not generate a message when a body is not
22956 @item ^-r^/TREE_FILE=REUSE^
22957 @cindex @option{^-r^/TREE_FILE=REUSE^} (@command{gnatstub})
22958 Reuse the tree file (if it exists) instead of creating it. Instead of
22959 creating the tree file for the library unit declaration, @command{gnatstub}
22960 tries to find it in the current directory and use it for creating
22961 a body. If the tree file is not found, no body is created. This option
22962 also implies @option{^-k^/SAVE^}, whether or not
22963 the latter is set explicitly.
22965 @item ^-t^/TREE_FILE=OVERWRITE^
22966 @cindex @option{^-t^/TREE_FILE=OVERWRITE^} (@command{gnatstub})
22967 Overwrite the existing tree file. If the current directory already
22968 contains the file which, according to the GNAT file naming rules should
22969 be considered as a tree file for the argument source file,
22971 will refuse to create the tree file needed to create a sample body
22972 unless this option is set.
22974 @item ^-v^/VERBOSE^
22975 @cindex @option{^-v^/VERBOSE^} (@command{gnatstub})
22976 Verbose mode: generate version information.
22980 @c *********************************
22981 @node Generating Ada Bindings for C and C++ headers
22982 @chapter Generating Ada Bindings for C and C++ headers
22986 GNAT now comes with a new experimental binding generator for C and C++
22987 headers which is intended to do 95% of the tedious work of generating
22988 Ada specs from C or C++ header files. Note that this still is a work in
22989 progress, not designed to generate 100% correct Ada specs.
22991 The code generated is using the Ada 2005 syntax, which makes it
22992 easier to interface with other languages than previous versions of Ada.
22995 * Running the binding generator::
22996 * Generating bindings for C++ headers::
23000 @node Running the binding generator
23001 @section Running the binding generator
23004 The binding generator is part of the @command{gcc} compiler and can be
23005 invoked via the @option{-fdump-ada-spec} switch, which will generate Ada
23006 spec files for the header files specified on the command line, and all
23007 header files needed by these files transitivitely. For example:
23010 $ g++ -c -fdump-ada-spec -C /usr/include/time.h
23011 $ gcc -c -gnat05 *.ads
23014 will generate, under GNU/Linux, the following files: @file{time_h.ads},
23015 @file{bits_time_h.ads}, @file{stddef_h.ads}, @file{bits_types_h.ads} which
23016 correspond to the files @file{/usr/include/time.h},
23017 @file{/usr/include/bits/time.h}, etc@dots{}, and will then compile in Ada 2005
23018 mode these Ada specs.
23020 The @code{-C} switch tells @command{gcc} to extract comments from headers,
23021 and will attempt to generate corresponding Ada comments.
23023 If you want to generate a single Ada file and not the transitive closure, you
23024 can use instead the @option{-fdump-ada-spec-slim} switch.
23026 Note that we recommend when possible to use the @command{g++} driver to
23027 generate bindings, even for most C headers, since this will in general
23028 generate better Ada specs. For generating bindings for C++ headers, it is
23029 mandatory to use the @command{g++} command, or @command{gcc -x c++} which
23030 is equivalent in this case. If @command{g++} cannot work on your C headers
23031 because of incompatibilities between C and C++, then you can fallback to
23032 @command{gcc} instead.
23034 For an example of better bindings generated from the C++ front-end,
23035 the name of the parameters (when available) are actually ignored by the C
23036 front-end. Consider the following C header:
23039 extern void foo (int variable);
23042 with the C front-end, @code{variable} is ignored, and the above is handled as:
23045 extern void foo (int);
23048 generating a generic:
23051 procedure foo (param1 : int);
23054 with the C++ front-end, the name is available, and we generate:
23057 procedure foo (variable : int);
23060 In some cases, the generated bindings will be more complete or more meaningful
23061 when defining some macros, which you can do via the @option{-D} switch. This
23062 is for example the case with @file{Xlib.h} under GNU/Linux:
23065 g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h
23068 The above will generate more complete bindings than a straight call without
23069 the @option{-DXLIB_ILLEGAL_ACCESS} switch.
23071 In other cases, it is not possible to parse a header file in a stand alone
23072 manner, because other include files need to be included first. In this
23073 case, the solution is to create a small header file including the needed
23074 @code{#include} and possible @code{#define} directives. For example, to
23075 generate Ada bindings for @file{readline/readline.h}, you need to first
23076 include @file{stdio.h}, so you can create a file with the following two
23077 lines in e.g. @file{readline1.h}:
23081 #include <readline/readline.h>
23084 and then generate Ada bindings from this file:
23087 $ g++ -c -fdump-ada-spec readline1.h
23090 @node Generating bindings for C++ headers
23091 @section Generating bindings for C++ headers
23094 Generating bindings for C++ headers is done using the same options, always
23095 with the @command{g++} compiler.
23097 In this mode, C++ classes will be mapped to Ada tagged types, constructors
23098 will be mapped using the @code{CPP_Constructor} pragma, and when possible,
23099 multiple inheritance of abstract classes will be mapped to Ada interfaces
23100 (@xref{Interfacing to C++,,,gnat_rm, GNAT Reference Manual}, for additional
23101 information on interfacing to C++).
23103 For example, given the following C++ header file:
23110 virtual int Number_Of_Teeth () = 0;
23115 virtual void Set_Owner (char* Name) = 0;
23121 virtual void Set_Age (int New_Age);
23124 class Dog : Animal, Carnivore, Domestic @{
23129 virtual int Number_Of_Teeth ();
23130 virtual void Set_Owner (char* Name);
23138 The corresponding Ada code is generated:
23140 @smallexample @c ada
23143 package Class_Carnivore is
23144 type Carnivore is limited interface;
23145 pragma Import (CPP, Carnivore);
23147 function Number_Of_Teeth (this : access Carnivore) return int is abstract;
23149 use Class_Carnivore;
23151 package Class_Domestic is
23152 type Domestic is limited interface;
23153 pragma Import (CPP, Domestic);
23155 procedure Set_Owner
23156 (this : access Domestic;
23157 Name : Interfaces.C.Strings.chars_ptr) is abstract;
23159 use Class_Domestic;
23161 package Class_Animal is
23162 type Animal is tagged limited record
23163 Age_Count : aliased int;
23165 pragma Import (CPP, Animal);
23167 procedure Set_Age (this : access Animal; New_Age : int);
23168 pragma Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi");
23172 package Class_Dog is
23173 type Dog is new Animal and Carnivore and Domestic with record
23174 Tooth_Count : aliased int;
23175 Owner : Interfaces.C.Strings.chars_ptr;
23177 pragma Import (CPP, Dog);
23179 function Number_Of_Teeth (this : access Dog) return int;
23180 pragma Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv");
23182 procedure Set_Owner
23183 (this : access Dog; Name : Interfaces.C.Strings.chars_ptr);
23184 pragma Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc");
23186 function New_Dog return Dog;
23187 pragma CPP_Constructor (New_Dog);
23188 pragma Import (CPP, New_Dog, "_ZN3DogC1Ev");
23199 @item -fdump-ada-spec
23200 @cindex @option{-fdump-ada-spec} (@command{gcc})
23201 Generate Ada spec files for the given header files transitively (including
23202 all header files that these headers depend upon).
23204 @item -fdump-ada-spec-slim
23205 @cindex @option{-fdump-ada-spec-slim} (@command{gcc})
23206 Generate Ada spec files for the header files specified on the command line
23210 @cindex @option{-C} (@command{gcc})
23211 Extract comments from headers and generate Ada comments in the Ada spec files.
23214 @node Other Utility Programs
23215 @chapter Other Utility Programs
23218 This chapter discusses some other utility programs available in the Ada
23222 * Using Other Utility Programs with GNAT::
23223 * The External Symbol Naming Scheme of GNAT::
23224 * Converting Ada Files to html with gnathtml::
23225 * Installing gnathtml::
23232 @node Using Other Utility Programs with GNAT
23233 @section Using Other Utility Programs with GNAT
23236 The object files generated by GNAT are in standard system format and in
23237 particular the debugging information uses this format. This means
23238 programs generated by GNAT can be used with existing utilities that
23239 depend on these formats.
23242 In general, any utility program that works with C will also often work with
23243 Ada programs generated by GNAT. This includes software utilities such as
23244 gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such
23248 @node The External Symbol Naming Scheme of GNAT
23249 @section The External Symbol Naming Scheme of GNAT
23252 In order to interpret the output from GNAT, when using tools that are
23253 originally intended for use with other languages, it is useful to
23254 understand the conventions used to generate link names from the Ada
23257 All link names are in all lowercase letters. With the exception of library
23258 procedure names, the mechanism used is simply to use the full expanded
23259 Ada name with dots replaced by double underscores. For example, suppose
23260 we have the following package spec:
23262 @smallexample @c ada
23273 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
23274 the corresponding link name is @code{qrs__mn}.
23276 Of course if a @code{pragma Export} is used this may be overridden:
23278 @smallexample @c ada
23283 pragma Export (Var1, C, External_Name => "var1_name");
23285 pragma Export (Var2, C, Link_Name => "var2_link_name");
23292 In this case, the link name for @var{Var1} is whatever link name the
23293 C compiler would assign for the C function @var{var1_name}. This typically
23294 would be either @var{var1_name} or @var{_var1_name}, depending on operating
23295 system conventions, but other possibilities exist. The link name for
23296 @var{Var2} is @var{var2_link_name}, and this is not operating system
23300 One exception occurs for library level procedures. A potential ambiguity
23301 arises between the required name @code{_main} for the C main program,
23302 and the name we would otherwise assign to an Ada library level procedure
23303 called @code{Main} (which might well not be the main program).
23305 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
23306 names. So if we have a library level procedure such as
23308 @smallexample @c ada
23311 procedure Hello (S : String);
23317 the external name of this procedure will be @var{_ada_hello}.
23320 @node Converting Ada Files to html with gnathtml
23321 @section Converting Ada Files to HTML with @code{gnathtml}
23324 This @code{Perl} script allows Ada source files to be browsed using
23325 standard Web browsers. For installation procedure, see the section
23326 @xref{Installing gnathtml}.
23328 Ada reserved keywords are highlighted in a bold font and Ada comments in
23329 a blue font. Unless your program was compiled with the gcc @option{-gnatx}
23330 switch to suppress the generation of cross-referencing information, user
23331 defined variables and types will appear in a different color; you will
23332 be able to click on any identifier and go to its declaration.
23334 The command line is as follow:
23336 $ perl gnathtml.pl @ovar{^switches^options^} @var{ada-files}
23340 You can pass it as many Ada files as you want. @code{gnathtml} will generate
23341 an html file for every ada file, and a global file called @file{index.htm}.
23342 This file is an index of every identifier defined in the files.
23344 The available ^switches^options^ are the following ones:
23348 @cindex @option{-83} (@code{gnathtml})
23349 Only the Ada 83 subset of keywords will be highlighted.
23351 @item -cc @var{color}
23352 @cindex @option{-cc} (@code{gnathtml})
23353 This option allows you to change the color used for comments. The default
23354 value is green. The color argument can be any name accepted by html.
23357 @cindex @option{-d} (@code{gnathtml})
23358 If the Ada files depend on some other files (for instance through
23359 @code{with} clauses, the latter files will also be converted to html.
23360 Only the files in the user project will be converted to html, not the files
23361 in the run-time library itself.
23364 @cindex @option{-D} (@code{gnathtml})
23365 This command is the same as @option{-d} above, but @command{gnathtml} will
23366 also look for files in the run-time library, and generate html files for them.
23368 @item -ext @var{extension}
23369 @cindex @option{-ext} (@code{gnathtml})
23370 This option allows you to change the extension of the generated HTML files.
23371 If you do not specify an extension, it will default to @file{htm}.
23374 @cindex @option{-f} (@code{gnathtml})
23375 By default, gnathtml will generate html links only for global entities
23376 ('with'ed units, global variables and types,@dots{}). If you specify
23377 @option{-f} on the command line, then links will be generated for local
23380 @item -l @var{number}
23381 @cindex @option{-l} (@code{gnathtml})
23382 If this ^switch^option^ is provided and @var{number} is not 0, then
23383 @code{gnathtml} will number the html files every @var{number} line.
23386 @cindex @option{-I} (@code{gnathtml})
23387 Specify a directory to search for library files (@file{.ALI} files) and
23388 source files. You can provide several -I switches on the command line,
23389 and the directories will be parsed in the order of the command line.
23392 @cindex @option{-o} (@code{gnathtml})
23393 Specify the output directory for html files. By default, gnathtml will
23394 saved the generated html files in a subdirectory named @file{html/}.
23396 @item -p @var{file}
23397 @cindex @option{-p} (@code{gnathtml})
23398 If you are using Emacs and the most recent Emacs Ada mode, which provides
23399 a full Integrated Development Environment for compiling, checking,
23400 running and debugging applications, you may use @file{.gpr} files
23401 to give the directories where Emacs can find sources and object files.
23403 Using this ^switch^option^, you can tell gnathtml to use these files.
23404 This allows you to get an html version of your application, even if it
23405 is spread over multiple directories.
23407 @item -sc @var{color}
23408 @cindex @option{-sc} (@code{gnathtml})
23409 This ^switch^option^ allows you to change the color used for symbol
23411 The default value is red. The color argument can be any name accepted by html.
23413 @item -t @var{file}
23414 @cindex @option{-t} (@code{gnathtml})
23415 This ^switch^option^ provides the name of a file. This file contains a list of
23416 file names to be converted, and the effect is exactly as though they had
23417 appeared explicitly on the command line. This
23418 is the recommended way to work around the command line length limit on some
23423 @node Installing gnathtml
23424 @section Installing @code{gnathtml}
23427 @code{Perl} needs to be installed on your machine to run this script.
23428 @code{Perl} is freely available for almost every architecture and
23429 Operating System via the Internet.
23431 On Unix systems, you may want to modify the first line of the script
23432 @code{gnathtml}, to explicitly tell the Operating system where Perl
23433 is. The syntax of this line is:
23435 #!full_path_name_to_perl
23439 Alternatively, you may run the script using the following command line:
23442 $ perl gnathtml.pl @ovar{switches} @var{files}
23451 The GNAT distribution provides an Ada 95 template for the HP Language
23452 Sensitive Editor (LSE), a component of DECset. In order to
23453 access it, invoke LSE with the qualifier /ENVIRONMENT=GNU:[LIB]ADA95.ENV.
23460 GNAT supports The HP Performance Coverage Analyzer (PCA), a component
23461 of DECset. To use it proceed as outlined under ``HELP PCA'', except for running
23462 the collection phase with the /DEBUG qualifier.
23465 $ GNAT MAKE /DEBUG <PROGRAM_NAME>
23466 $ DEFINE LIB$DEBUG PCA$COLLECTOR
23467 $ RUN/DEBUG <PROGRAM_NAME>
23473 @c ******************************
23474 @node Code Coverage and Profiling
23475 @chapter Code Coverage and Profiling
23476 @cindex Code Coverage
23480 This chapter describes how to use @code{gcov} - coverage testing tool - and
23481 @code{gprof} - profiler tool - on your Ada programs.
23484 * Code Coverage of Ada Programs using gcov::
23485 * Profiling an Ada Program using gprof::
23488 @node Code Coverage of Ada Programs using gcov
23489 @section Code Coverage of Ada Programs using gcov
23491 @cindex -fprofile-arcs
23492 @cindex -ftest-coverage
23494 @cindex Code Coverage
23497 @code{gcov} is a test coverage program: it analyzes the execution of a given
23498 program on selected tests, to help you determine the portions of the program
23499 that are still untested.
23501 @code{gcov} is part of the GCC suite, and is described in detail in the GCC
23502 User's Guide. You can refer to this documentation for a more complete
23505 This chapter provides a quick startup guide, and
23506 details some Gnat-specific features.
23509 * Quick startup guide::
23513 @node Quick startup guide
23514 @subsection Quick startup guide
23516 In order to perform coverage analysis of a program using @code{gcov}, 3
23521 Code instrumentation during the compilation process
23523 Execution of the instrumented program
23525 Execution of the @code{gcov} tool to generate the result.
23528 The code instrumentation needed by gcov is created at the object level:
23529 The source code is not modified in any way, because the instrumentation code is
23530 inserted by gcc during the compilation process. To compile your code with code
23531 coverage activated, you need to recompile your whole project using the
23533 @code{-fprofile-arcs} and @code{-ftest-coverage}, and link it using
23534 @code{-fprofile-arcs}.
23537 $ gnatmake -P my_project.gpr -f -cargs -fprofile-arcs -ftest-coverage \
23538 -largs -fprofile-arcs
23541 This compilation process will create @file{.gcno} files together with
23542 the usual object files.
23544 Once the program is compiled with coverage instrumentation, you can
23545 run it as many times as needed - on portions of a test suite for
23546 example. The first execution will produce @file{.gcda} files at the
23547 same location as the @file{.gcno} files. The following executions
23548 will update those files, so that a cumulative result of the covered
23549 portions of the program is generated.
23551 Finally, you need to call the @code{gcov} tool. The different options of
23552 @code{gcov} are available in the GCC User's Guide, section 'Invoking gcov'.
23554 This will create annotated source files with a @file{.gcov} extension:
23555 @file{my_main.adb} file will be analysed in @file{my_main.adb.gcov}.
23557 @node Gnat specifics
23558 @subsection Gnat specifics
23560 Because Ada semantics, portions of the source code may be shared among
23561 several object files. This is the case for example when generics are
23562 involved, when inlining is active or when declarations generate initialisation
23563 calls. In order to take
23564 into account this shared code, you need to call @code{gcov} on all
23565 source files of the tested program at once.
23567 The list of source files might exceed the system's maximum command line
23568 length. In order to bypass this limitation, a new mechanism has been
23569 implemented in @code{gcov}: you can now list all your project's files into a
23570 text file, and provide this file to gcov as a parameter, preceded by a @@
23571 (e.g. @samp{gcov @@mysrclist.txt}).
23573 Note that on AIX compiling a static library with @code{-fprofile-arcs} is
23574 not supported as there can be unresolved symbols during the final link.
23576 @node Profiling an Ada Program using gprof
23577 @section Profiling an Ada Program using gprof
23583 This section is not meant to be an exhaustive documentation of @code{gprof}.
23584 Full documentation for it can be found in the GNU Profiler User's Guide
23585 documentation that is part of this GNAT distribution.
23587 Profiling a program helps determine the parts of a program that are executed
23588 most often, and are therefore the most time-consuming.
23590 @code{gprof} is the standard GNU profiling tool; it has been enhanced to
23591 better handle Ada programs and multitasking.
23592 It is currently supported on the following platforms
23597 solaris sparc/sparc64/x86
23603 In order to profile a program using @code{gprof}, 3 steps are needed:
23607 Code instrumentation, requiring a full recompilation of the project with the
23610 Execution of the program under the analysis conditions, i.e. with the desired
23613 Analysis of the results using the @code{gprof} tool.
23617 The following sections detail the different steps, and indicate how
23618 to interpret the results:
23620 * Compilation for profiling::
23621 * Program execution::
23623 * Interpretation of profiling results::
23626 @node Compilation for profiling
23627 @subsection Compilation for profiling
23631 In order to profile a program the first step is to tell the compiler
23632 to generate the necessary profiling information. The compiler switch to be used
23633 is @code{-pg}, which must be added to other compilation switches. This
23634 switch needs to be specified both during compilation and link stages, and can
23635 be specified once when using gnatmake:
23638 gnatmake -f -pg -P my_project
23642 Note that only the objects that were compiled with the @samp{-pg} switch will be
23643 profiled; if you need to profile your whole project, use the
23644 @samp{-f} gnatmake switch to force full recompilation.
23646 @node Program execution
23647 @subsection Program execution
23650 Once the program has been compiled for profiling, you can run it as usual.
23652 The only constraint imposed by profiling is that the program must terminate
23653 normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be
23656 Once the program completes execution, a data file called @file{gmon.out} is
23657 generated in the directory where the program was launched from. If this file
23658 already exists, it will be overwritten.
23660 @node Running gprof
23661 @subsection Running gprof
23664 The @code{gprof} tool is called as follow:
23667 gprof my_prog gmon.out
23678 The complete form of the gprof command line is the following:
23681 gprof [^switches^options^] [executable [data-file]]
23685 @code{gprof} supports numerous ^switch^options^. The order of these
23686 ^switch^options^ does not matter. The full list of options can be found in
23687 the GNU Profiler User's Guide documentation that comes with this documentation.
23689 The following is the subset of those switches that is most relevant:
23693 @item --demangle[=@var{style}]
23694 @itemx --no-demangle
23695 @cindex @option{--demangle} (@code{gprof})
23696 These options control whether symbol names should be demangled when
23697 printing output. The default is to demangle C++ symbols. The
23698 @code{--no-demangle} option may be used to turn off demangling. Different
23699 compilers have different mangling styles. The optional demangling style
23700 argument can be used to choose an appropriate demangling style for your
23701 compiler, in particular Ada symbols generated by GNAT can be demangled using
23702 @code{--demangle=gnat}.
23704 @item -e @var{function_name}
23705 @cindex @option{-e} (@code{gprof})
23706 The @samp{-e @var{function}} option tells @code{gprof} not to print
23707 information about the function @var{function_name} (and its
23708 children@dots{}) in the call graph. The function will still be listed
23709 as a child of any functions that call it, but its index number will be
23710 shown as @samp{[not printed]}. More than one @samp{-e} option may be
23711 given; only one @var{function_name} may be indicated with each @samp{-e}
23714 @item -E @var{function_name}
23715 @cindex @option{-E} (@code{gprof})
23716 The @code{-E @var{function}} option works like the @code{-e} option, but
23717 execution time spent in the function (and children who were not called from
23718 anywhere else), will not be used to compute the percentages-of-time for
23719 the call graph. More than one @samp{-E} option may be given; only one
23720 @var{function_name} may be indicated with each @samp{-E} option.
23722 @item -f @var{function_name}
23723 @cindex @option{-f} (@code{gprof})
23724 The @samp{-f @var{function}} option causes @code{gprof} to limit the
23725 call graph to the function @var{function_name} and its children (and
23726 their children@dots{}). More than one @samp{-f} option may be given;
23727 only one @var{function_name} may be indicated with each @samp{-f}
23730 @item -F @var{function_name}
23731 @cindex @option{-F} (@code{gprof})
23732 The @samp{-F @var{function}} option works like the @code{-f} option, but
23733 only time spent in the function and its children (and their
23734 children@dots{}) will be used to determine total-time and
23735 percentages-of-time for the call graph. More than one @samp{-F} option
23736 may be given; only one @var{function_name} may be indicated with each
23737 @samp{-F} option. The @samp{-F} option overrides the @samp{-E} option.
23741 @node Interpretation of profiling results
23742 @subsection Interpretation of profiling results
23746 The results of the profiling analysis are represented by two arrays: the
23747 'flat profile' and the 'call graph'. Full documentation of those outputs
23748 can be found in the GNU Profiler User's Guide.
23750 The flat profile shows the time spent in each function of the program, and how
23751 many time it has been called. This allows you to locate easily the most
23752 time-consuming functions.
23754 The call graph shows, for each subprogram, the subprograms that call it,
23755 and the subprograms that it calls. It also provides an estimate of the time
23756 spent in each of those callers/called subprograms.
23759 @c ******************************
23760 @node Running and Debugging Ada Programs
23761 @chapter Running and Debugging Ada Programs
23765 This chapter discusses how to debug Ada programs.
23767 It applies to GNAT on the Alpha OpenVMS platform;
23768 for I64 OpenVMS please refer to the @cite{OpenVMS Debugger Manual},
23769 since HP has implemented Ada support in the OpenVMS debugger on I64.
23772 An incorrect Ada program may be handled in three ways by the GNAT compiler:
23776 The illegality may be a violation of the static semantics of Ada. In
23777 that case GNAT diagnoses the constructs in the program that are illegal.
23778 It is then a straightforward matter for the user to modify those parts of
23782 The illegality may be a violation of the dynamic semantics of Ada. In
23783 that case the program compiles and executes, but may generate incorrect
23784 results, or may terminate abnormally with some exception.
23787 When presented with a program that contains convoluted errors, GNAT
23788 itself may terminate abnormally without providing full diagnostics on
23789 the incorrect user program.
23793 * The GNAT Debugger GDB::
23795 * Introduction to GDB Commands::
23796 * Using Ada Expressions::
23797 * Calling User-Defined Subprograms::
23798 * Using the Next Command in a Function::
23801 * Debugging Generic Units::
23802 * GNAT Abnormal Termination or Failure to Terminate::
23803 * Naming Conventions for GNAT Source Files::
23804 * Getting Internal Debugging Information::
23805 * Stack Traceback::
23811 @node The GNAT Debugger GDB
23812 @section The GNAT Debugger GDB
23815 @code{GDB} is a general purpose, platform-independent debugger that
23816 can be used to debug mixed-language programs compiled with @command{gcc},
23817 and in particular is capable of debugging Ada programs compiled with
23818 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
23819 complex Ada data structures.
23821 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
23823 located in the GNU:[DOCS] directory,
23825 for full details on the usage of @code{GDB}, including a section on
23826 its usage on programs. This manual should be consulted for full
23827 details. The section that follows is a brief introduction to the
23828 philosophy and use of @code{GDB}.
23830 When GNAT programs are compiled, the compiler optionally writes debugging
23831 information into the generated object file, including information on
23832 line numbers, and on declared types and variables. This information is
23833 separate from the generated code. It makes the object files considerably
23834 larger, but it does not add to the size of the actual executable that
23835 will be loaded into memory, and has no impact on run-time performance. The
23836 generation of debug information is triggered by the use of the
23837 ^-g^/DEBUG^ switch in the @command{gcc} or @command{gnatmake} command
23838 used to carry out the compilations. It is important to emphasize that
23839 the use of these options does not change the generated code.
23841 The debugging information is written in standard system formats that
23842 are used by many tools, including debuggers and profilers. The format
23843 of the information is typically designed to describe C types and
23844 semantics, but GNAT implements a translation scheme which allows full
23845 details about Ada types and variables to be encoded into these
23846 standard C formats. Details of this encoding scheme may be found in
23847 the file exp_dbug.ads in the GNAT source distribution. However, the
23848 details of this encoding are, in general, of no interest to a user,
23849 since @code{GDB} automatically performs the necessary decoding.
23851 When a program is bound and linked, the debugging information is
23852 collected from the object files, and stored in the executable image of
23853 the program. Again, this process significantly increases the size of
23854 the generated executable file, but it does not increase the size of
23855 the executable program itself. Furthermore, if this program is run in
23856 the normal manner, it runs exactly as if the debug information were
23857 not present, and takes no more actual memory.
23859 However, if the program is run under control of @code{GDB}, the
23860 debugger is activated. The image of the program is loaded, at which
23861 point it is ready to run. If a run command is given, then the program
23862 will run exactly as it would have if @code{GDB} were not present. This
23863 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
23864 entirely non-intrusive until a breakpoint is encountered. If no
23865 breakpoint is ever hit, the program will run exactly as it would if no
23866 debugger were present. When a breakpoint is hit, @code{GDB} accesses
23867 the debugging information and can respond to user commands to inspect
23868 variables, and more generally to report on the state of execution.
23872 @section Running GDB
23875 This section describes how to initiate the debugger.
23876 @c The above sentence is really just filler, but it was otherwise
23877 @c clumsy to get the first paragraph nonindented given the conditional
23878 @c nature of the description
23881 The debugger can be launched from a @code{GPS} menu or
23882 directly from the command line. The description below covers the latter use.
23883 All the commands shown can be used in the @code{GPS} debug console window,
23884 but there are usually more GUI-based ways to achieve the same effect.
23887 The command to run @code{GDB} is
23890 $ ^gdb program^GDB PROGRAM^
23894 where @code{^program^PROGRAM^} is the name of the executable file. This
23895 activates the debugger and results in a prompt for debugger commands.
23896 The simplest command is simply @code{run}, which causes the program to run
23897 exactly as if the debugger were not present. The following section
23898 describes some of the additional commands that can be given to @code{GDB}.
23900 @c *******************************
23901 @node Introduction to GDB Commands
23902 @section Introduction to GDB Commands
23905 @code{GDB} contains a large repertoire of commands. @xref{Top,,
23906 Debugging with GDB, gdb, Debugging with GDB},
23908 located in the GNU:[DOCS] directory,
23910 for extensive documentation on the use
23911 of these commands, together with examples of their use. Furthermore,
23912 the command @command{help} invoked from within GDB activates a simple help
23913 facility which summarizes the available commands and their options.
23914 In this section we summarize a few of the most commonly
23915 used commands to give an idea of what @code{GDB} is about. You should create
23916 a simple program with debugging information and experiment with the use of
23917 these @code{GDB} commands on the program as you read through the
23921 @item set args @var{arguments}
23922 The @var{arguments} list above is a list of arguments to be passed to
23923 the program on a subsequent run command, just as though the arguments
23924 had been entered on a normal invocation of the program. The @code{set args}
23925 command is not needed if the program does not require arguments.
23928 The @code{run} command causes execution of the program to start from
23929 the beginning. If the program is already running, that is to say if
23930 you are currently positioned at a breakpoint, then a prompt will ask
23931 for confirmation that you want to abandon the current execution and
23934 @item breakpoint @var{location}
23935 The breakpoint command sets a breakpoint, that is to say a point at which
23936 execution will halt and @code{GDB} will await further
23937 commands. @var{location} is
23938 either a line number within a file, given in the format @code{file:linenumber},
23939 or it is the name of a subprogram. If you request that a breakpoint be set on
23940 a subprogram that is overloaded, a prompt will ask you to specify on which of
23941 those subprograms you want to breakpoint. You can also
23942 specify that all of them should be breakpointed. If the program is run
23943 and execution encounters the breakpoint, then the program
23944 stops and @code{GDB} signals that the breakpoint was encountered by
23945 printing the line of code before which the program is halted.
23947 @item breakpoint exception @var{name}
23948 A special form of the breakpoint command which breakpoints whenever
23949 exception @var{name} is raised.
23950 If @var{name} is omitted,
23951 then a breakpoint will occur when any exception is raised.
23953 @item print @var{expression}
23954 This will print the value of the given expression. Most simple
23955 Ada expression formats are properly handled by @code{GDB}, so the expression
23956 can contain function calls, variables, operators, and attribute references.
23959 Continues execution following a breakpoint, until the next breakpoint or the
23960 termination of the program.
23963 Executes a single line after a breakpoint. If the next statement
23964 is a subprogram call, execution continues into (the first statement of)
23965 the called subprogram.
23968 Executes a single line. If this line is a subprogram call, executes and
23969 returns from the call.
23972 Lists a few lines around the current source location. In practice, it
23973 is usually more convenient to have a separate edit window open with the
23974 relevant source file displayed. Successive applications of this command
23975 print subsequent lines. The command can be given an argument which is a
23976 line number, in which case it displays a few lines around the specified one.
23979 Displays a backtrace of the call chain. This command is typically
23980 used after a breakpoint has occurred, to examine the sequence of calls that
23981 leads to the current breakpoint. The display includes one line for each
23982 activation record (frame) corresponding to an active subprogram.
23985 At a breakpoint, @code{GDB} can display the values of variables local
23986 to the current frame. The command @code{up} can be used to
23987 examine the contents of other active frames, by moving the focus up
23988 the stack, that is to say from callee to caller, one frame at a time.
23991 Moves the focus of @code{GDB} down from the frame currently being
23992 examined to the frame of its callee (the reverse of the previous command),
23994 @item frame @var{n}
23995 Inspect the frame with the given number. The value 0 denotes the frame
23996 of the current breakpoint, that is to say the top of the call stack.
24001 The above list is a very short introduction to the commands that
24002 @code{GDB} provides. Important additional capabilities, including conditional
24003 breakpoints, the ability to execute command sequences on a breakpoint,
24004 the ability to debug at the machine instruction level and many other
24005 features are described in detail in @ref{Top,, Debugging with GDB, gdb,
24006 Debugging with GDB}. Note that most commands can be abbreviated
24007 (for example, c for continue, bt for backtrace).
24009 @node Using Ada Expressions
24010 @section Using Ada Expressions
24011 @cindex Ada expressions
24014 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
24015 extensions. The philosophy behind the design of this subset is
24019 That @code{GDB} should provide basic literals and access to operations for
24020 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
24021 leaving more sophisticated computations to subprograms written into the
24022 program (which therefore may be called from @code{GDB}).
24025 That type safety and strict adherence to Ada language restrictions
24026 are not particularly important to the @code{GDB} user.
24029 That brevity is important to the @code{GDB} user.
24033 Thus, for brevity, the debugger acts as if there were
24034 implicit @code{with} and @code{use} clauses in effect for all user-written
24035 packages, thus making it unnecessary to fully qualify most names with
24036 their packages, regardless of context. Where this causes ambiguity,
24037 @code{GDB} asks the user's intent.
24039 For details on the supported Ada syntax, see @ref{Top,, Debugging with
24040 GDB, gdb, Debugging with GDB}.
24042 @node Calling User-Defined Subprograms
24043 @section Calling User-Defined Subprograms
24046 An important capability of @code{GDB} is the ability to call user-defined
24047 subprograms while debugging. This is achieved simply by entering
24048 a subprogram call statement in the form:
24051 call subprogram-name (parameters)
24055 The keyword @code{call} can be omitted in the normal case where the
24056 @code{subprogram-name} does not coincide with any of the predefined
24057 @code{GDB} commands.
24059 The effect is to invoke the given subprogram, passing it the
24060 list of parameters that is supplied. The parameters can be expressions and
24061 can include variables from the program being debugged. The
24062 subprogram must be defined
24063 at the library level within your program, and @code{GDB} will call the
24064 subprogram within the environment of your program execution (which
24065 means that the subprogram is free to access or even modify variables
24066 within your program).
24068 The most important use of this facility is in allowing the inclusion of
24069 debugging routines that are tailored to particular data structures
24070 in your program. Such debugging routines can be written to provide a suitably
24071 high-level description of an abstract type, rather than a low-level dump
24072 of its physical layout. After all, the standard
24073 @code{GDB print} command only knows the physical layout of your
24074 types, not their abstract meaning. Debugging routines can provide information
24075 at the desired semantic level and are thus enormously useful.
24077 For example, when debugging GNAT itself, it is crucial to have access to
24078 the contents of the tree nodes used to represent the program internally.
24079 But tree nodes are represented simply by an integer value (which in turn
24080 is an index into a table of nodes).
24081 Using the @code{print} command on a tree node would simply print this integer
24082 value, which is not very useful. But the PN routine (defined in file
24083 treepr.adb in the GNAT sources) takes a tree node as input, and displays
24084 a useful high level representation of the tree node, which includes the
24085 syntactic category of the node, its position in the source, the integers
24086 that denote descendant nodes and parent node, as well as varied
24087 semantic information. To study this example in more detail, you might want to
24088 look at the body of the PN procedure in the stated file.
24090 @node Using the Next Command in a Function
24091 @section Using the Next Command in a Function
24094 When you use the @code{next} command in a function, the current source
24095 location will advance to the next statement as usual. A special case
24096 arises in the case of a @code{return} statement.
24098 Part of the code for a return statement is the ``epilog'' of the function.
24099 This is the code that returns to the caller. There is only one copy of
24100 this epilog code, and it is typically associated with the last return
24101 statement in the function if there is more than one return. In some
24102 implementations, this epilog is associated with the first statement
24105 The result is that if you use the @code{next} command from a return
24106 statement that is not the last return statement of the function you
24107 may see a strange apparent jump to the last return statement or to
24108 the start of the function. You should simply ignore this odd jump.
24109 The value returned is always that from the first return statement
24110 that was stepped through.
24112 @node Ada Exceptions
24113 @section Breaking on Ada Exceptions
24117 You can set breakpoints that trip when your program raises
24118 selected exceptions.
24121 @item break exception
24122 Set a breakpoint that trips whenever (any task in the) program raises
24125 @item break exception @var{name}
24126 Set a breakpoint that trips whenever (any task in the) program raises
24127 the exception @var{name}.
24129 @item break exception unhandled
24130 Set a breakpoint that trips whenever (any task in the) program raises an
24131 exception for which there is no handler.
24133 @item info exceptions
24134 @itemx info exceptions @var{regexp}
24135 The @code{info exceptions} command permits the user to examine all defined
24136 exceptions within Ada programs. With a regular expression, @var{regexp}, as
24137 argument, prints out only those exceptions whose name matches @var{regexp}.
24145 @code{GDB} allows the following task-related commands:
24149 This command shows a list of current Ada tasks, as in the following example:
24156 ID TID P-ID Thread Pri State Name
24157 1 8088000 0 807e000 15 Child Activation Wait main_task
24158 2 80a4000 1 80ae000 15 Accept/Select Wait b
24159 3 809a800 1 80a4800 15 Child Activation Wait a
24160 * 4 80ae800 3 80b8000 15 Running c
24164 In this listing, the asterisk before the first task indicates it to be the
24165 currently running task. The first column lists the task ID that is used
24166 to refer to tasks in the following commands.
24168 @item break @var{linespec} task @var{taskid}
24169 @itemx break @var{linespec} task @var{taskid} if @dots{}
24170 @cindex Breakpoints and tasks
24171 These commands are like the @code{break @dots{} thread @dots{}}.
24172 @var{linespec} specifies source lines.
24174 Use the qualifier @samp{task @var{taskid}} with a breakpoint command
24175 to specify that you only want @code{GDB} to stop the program when a
24176 particular Ada task reaches this breakpoint. @var{taskid} is one of the
24177 numeric task identifiers assigned by @code{GDB}, shown in the first
24178 column of the @samp{info tasks} display.
24180 If you do not specify @samp{task @var{taskid}} when you set a
24181 breakpoint, the breakpoint applies to @emph{all} tasks of your
24184 You can use the @code{task} qualifier on conditional breakpoints as
24185 well; in this case, place @samp{task @var{taskid}} before the
24186 breakpoint condition (before the @code{if}).
24188 @item task @var{taskno}
24189 @cindex Task switching
24191 This command allows to switch to the task referred by @var{taskno}. In
24192 particular, This allows to browse the backtrace of the specified
24193 task. It is advised to switch back to the original task before
24194 continuing execution otherwise the scheduling of the program may be
24199 For more detailed information on the tasking support,
24200 see @ref{Top,, Debugging with GDB, gdb, Debugging with GDB}.
24202 @node Debugging Generic Units
24203 @section Debugging Generic Units
24204 @cindex Debugging Generic Units
24208 GNAT always uses code expansion for generic instantiation. This means that
24209 each time an instantiation occurs, a complete copy of the original code is
24210 made, with appropriate substitutions of formals by actuals.
24212 It is not possible to refer to the original generic entities in
24213 @code{GDB}, but it is always possible to debug a particular instance of
24214 a generic, by using the appropriate expanded names. For example, if we have
24216 @smallexample @c ada
24221 generic package k is
24222 procedure kp (v1 : in out integer);
24226 procedure kp (v1 : in out integer) is
24232 package k1 is new k;
24233 package k2 is new k;
24235 var : integer := 1;
24248 Then to break on a call to procedure kp in the k2 instance, simply
24252 (gdb) break g.k2.kp
24256 When the breakpoint occurs, you can step through the code of the
24257 instance in the normal manner and examine the values of local variables, as for
24260 @node GNAT Abnormal Termination or Failure to Terminate
24261 @section GNAT Abnormal Termination or Failure to Terminate
24262 @cindex GNAT Abnormal Termination or Failure to Terminate
24265 When presented with programs that contain serious errors in syntax
24267 GNAT may on rare occasions experience problems in operation, such
24269 segmentation fault or illegal memory access, raising an internal
24270 exception, terminating abnormally, or failing to terminate at all.
24271 In such cases, you can activate
24272 various features of GNAT that can help you pinpoint the construct in your
24273 program that is the likely source of the problem.
24275 The following strategies are presented in increasing order of
24276 difficulty, corresponding to your experience in using GNAT and your
24277 familiarity with compiler internals.
24281 Run @command{gcc} with the @option{-gnatf}. This first
24282 switch causes all errors on a given line to be reported. In its absence,
24283 only the first error on a line is displayed.
24285 The @option{-gnatdO} switch causes errors to be displayed as soon as they
24286 are encountered, rather than after compilation is terminated. If GNAT
24287 terminates prematurely or goes into an infinite loop, the last error
24288 message displayed may help to pinpoint the culprit.
24291 Run @command{gcc} with the @option{^-v (verbose)^/VERBOSE^} switch. In this
24292 mode, @command{gcc} produces ongoing information about the progress of the
24293 compilation and provides the name of each procedure as code is
24294 generated. This switch allows you to find which Ada procedure was being
24295 compiled when it encountered a code generation problem.
24298 @cindex @option{-gnatdc} switch
24299 Run @command{gcc} with the @option{-gnatdc} switch. This is a GNAT specific
24300 switch that does for the front-end what @option{^-v^VERBOSE^} does
24301 for the back end. The system prints the name of each unit,
24302 either a compilation unit or nested unit, as it is being analyzed.
24304 Finally, you can start
24305 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
24306 front-end of GNAT, and can be run independently (normally it is just
24307 called from @command{gcc}). You can use @code{gdb} on @code{gnat1} as you
24308 would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The
24309 @code{where} command is the first line of attack; the variable
24310 @code{lineno} (seen by @code{print lineno}), used by the second phase of
24311 @code{gnat1} and by the @command{gcc} backend, indicates the source line at
24312 which the execution stopped, and @code{input_file name} indicates the name of
24316 @node Naming Conventions for GNAT Source Files
24317 @section Naming Conventions for GNAT Source Files
24320 In order to examine the workings of the GNAT system, the following
24321 brief description of its organization may be helpful:
24325 Files with prefix @file{^sc^SC^} contain the lexical scanner.
24328 All files prefixed with @file{^par^PAR^} are components of the parser. The
24329 numbers correspond to chapters of the Ada Reference Manual. For example,
24330 parsing of select statements can be found in @file{par-ch9.adb}.
24333 All files prefixed with @file{^sem^SEM^} perform semantic analysis. The
24334 numbers correspond to chapters of the Ada standard. For example, all
24335 issues involving context clauses can be found in @file{sem_ch10.adb}. In
24336 addition, some features of the language require sufficient special processing
24337 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
24338 dynamic dispatching, etc.
24341 All files prefixed with @file{^exp^EXP^} perform normalization and
24342 expansion of the intermediate representation (abstract syntax tree, or AST).
24343 these files use the same numbering scheme as the parser and semantics files.
24344 For example, the construction of record initialization procedures is done in
24345 @file{exp_ch3.adb}.
24348 The files prefixed with @file{^bind^BIND^} implement the binder, which
24349 verifies the consistency of the compilation, determines an order of
24350 elaboration, and generates the bind file.
24353 The files @file{atree.ads} and @file{atree.adb} detail the low-level
24354 data structures used by the front-end.
24357 The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of
24358 the abstract syntax tree as produced by the parser.
24361 The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of
24362 all entities, computed during semantic analysis.
24365 Library management issues are dealt with in files with prefix
24371 Ada files with the prefix @file{^a-^A-^} are children of @code{Ada}, as
24372 defined in Annex A.
24377 Files with prefix @file{^i-^I-^} are children of @code{Interfaces}, as
24378 defined in Annex B.
24382 Files with prefix @file{^s-^S-^} are children of @code{System}. This includes
24383 both language-defined children and GNAT run-time routines.
24387 Files with prefix @file{^g-^G-^} are children of @code{GNAT}. These are useful
24388 general-purpose packages, fully documented in their specs. All
24389 the other @file{.c} files are modifications of common @command{gcc} files.
24392 @node Getting Internal Debugging Information
24393 @section Getting Internal Debugging Information
24396 Most compilers have internal debugging switches and modes. GNAT
24397 does also, except GNAT internal debugging switches and modes are not
24398 secret. A summary and full description of all the compiler and binder
24399 debug flags are in the file @file{debug.adb}. You must obtain the
24400 sources of the compiler to see the full detailed effects of these flags.
24402 The switches that print the source of the program (reconstructed from
24403 the internal tree) are of general interest for user programs, as are the
24405 the full internal tree, and the entity table (the symbol table
24406 information). The reconstructed source provides a readable version of the
24407 program after the front-end has completed analysis and expansion,
24408 and is useful when studying the performance of specific constructs.
24409 For example, constraint checks are indicated, complex aggregates
24410 are replaced with loops and assignments, and tasking primitives
24411 are replaced with run-time calls.
24413 @node Stack Traceback
24414 @section Stack Traceback
24416 @cindex stack traceback
24417 @cindex stack unwinding
24420 Traceback is a mechanism to display the sequence of subprogram calls that
24421 leads to a specified execution point in a program. Often (but not always)
24422 the execution point is an instruction at which an exception has been raised.
24423 This mechanism is also known as @i{stack unwinding} because it obtains
24424 its information by scanning the run-time stack and recovering the activation
24425 records of all active subprograms. Stack unwinding is one of the most
24426 important tools for program debugging.
24428 The first entry stored in traceback corresponds to the deepest calling level,
24429 that is to say the subprogram currently executing the instruction
24430 from which we want to obtain the traceback.
24432 Note that there is no runtime performance penalty when stack traceback
24433 is enabled, and no exception is raised during program execution.
24436 * Non-Symbolic Traceback::
24437 * Symbolic Traceback::
24440 @node Non-Symbolic Traceback
24441 @subsection Non-Symbolic Traceback
24442 @cindex traceback, non-symbolic
24445 Note: this feature is not supported on all platforms. See
24446 @file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported
24450 * Tracebacks From an Unhandled Exception::
24451 * Tracebacks From Exception Occurrences (non-symbolic)::
24452 * Tracebacks From Anywhere in a Program (non-symbolic)::
24455 @node Tracebacks From an Unhandled Exception
24456 @subsubsection Tracebacks From an Unhandled Exception
24459 A runtime non-symbolic traceback is a list of addresses of call instructions.
24460 To enable this feature you must use the @option{-E}
24461 @code{gnatbind}'s option. With this option a stack traceback is stored as part
24462 of exception information. You can retrieve this information using the
24463 @code{addr2line} tool.
24465 Here is a simple example:
24467 @smallexample @c ada
24473 raise Constraint_Error;
24488 $ gnatmake stb -bargs -E
24491 Execution terminated by unhandled exception
24492 Exception name: CONSTRAINT_ERROR
24494 Call stack traceback locations:
24495 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
24499 As we see the traceback lists a sequence of addresses for the unhandled
24500 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
24501 guess that this exception come from procedure P1. To translate these
24502 addresses into the source lines where the calls appear, the
24503 @code{addr2line} tool, described below, is invaluable. The use of this tool
24504 requires the program to be compiled with debug information.
24507 $ gnatmake -g stb -bargs -E
24510 Execution terminated by unhandled exception
24511 Exception name: CONSTRAINT_ERROR
24513 Call stack traceback locations:
24514 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
24516 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
24517 0x4011f1 0x77e892a4
24519 00401373 at d:/stb/stb.adb:5
24520 0040138B at d:/stb/stb.adb:10
24521 0040139C at d:/stb/stb.adb:14
24522 00401335 at d:/stb/b~stb.adb:104
24523 004011C4 at /build/@dots{}/crt1.c:200
24524 004011F1 at /build/@dots{}/crt1.c:222
24525 77E892A4 in ?? at ??:0
24529 The @code{addr2line} tool has several other useful options:
24533 to get the function name corresponding to any location
24535 @item --demangle=gnat
24536 to use the gnat decoding mode for the function names. Note that
24537 for binutils version 2.9.x the option is simply @option{--demangle}.
24541 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
24542 0x40139c 0x401335 0x4011c4 0x4011f1
24544 00401373 in stb.p1 at d:/stb/stb.adb:5
24545 0040138B in stb.p2 at d:/stb/stb.adb:10
24546 0040139C in stb at d:/stb/stb.adb:14
24547 00401335 in main at d:/stb/b~stb.adb:104
24548 004011C4 in <__mingw_CRTStartup> at /build/@dots{}/crt1.c:200
24549 004011F1 in <mainCRTStartup> at /build/@dots{}/crt1.c:222
24553 From this traceback we can see that the exception was raised in
24554 @file{stb.adb} at line 5, which was reached from a procedure call in
24555 @file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file,
24556 which contains the call to the main program.
24557 @xref{Running gnatbind}. The remaining entries are assorted runtime routines,
24558 and the output will vary from platform to platform.
24560 It is also possible to use @code{GDB} with these traceback addresses to debug
24561 the program. For example, we can break at a given code location, as reported
24562 in the stack traceback:
24568 Furthermore, this feature is not implemented inside Windows DLL. Only
24569 the non-symbolic traceback is reported in this case.
24572 (gdb) break *0x401373
24573 Breakpoint 1 at 0x401373: file stb.adb, line 5.
24577 It is important to note that the stack traceback addresses
24578 do not change when debug information is included. This is particularly useful
24579 because it makes it possible to release software without debug information (to
24580 minimize object size), get a field report that includes a stack traceback
24581 whenever an internal bug occurs, and then be able to retrieve the sequence
24582 of calls with the same program compiled with debug information.
24584 @node Tracebacks From Exception Occurrences (non-symbolic)
24585 @subsubsection Tracebacks From Exception Occurrences
24588 Non-symbolic tracebacks are obtained by using the @option{-E} binder argument.
24589 The stack traceback is attached to the exception information string, and can
24590 be retrieved in an exception handler within the Ada program, by means of the
24591 Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example:
24593 @smallexample @c ada
24595 with Ada.Exceptions;
24600 use Ada.Exceptions;
24608 Text_IO.Put_Line (Exception_Information (E));
24622 This program will output:
24627 Exception name: CONSTRAINT_ERROR
24628 Message: stb.adb:12
24629 Call stack traceback locations:
24630 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
24633 @node Tracebacks From Anywhere in a Program (non-symbolic)
24634 @subsubsection Tracebacks From Anywhere in a Program
24637 It is also possible to retrieve a stack traceback from anywhere in a
24638 program. For this you need to
24639 use the @code{GNAT.Traceback} API. This package includes a procedure called
24640 @code{Call_Chain} that computes a complete stack traceback, as well as useful
24641 display procedures described below. It is not necessary to use the
24642 @option{-E gnatbind} option in this case, because the stack traceback mechanism
24643 is invoked explicitly.
24646 In the following example we compute a traceback at a specific location in
24647 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
24648 convert addresses to strings:
24650 @smallexample @c ada
24652 with GNAT.Traceback;
24653 with GNAT.Debug_Utilities;
24659 use GNAT.Traceback;
24662 TB : Tracebacks_Array (1 .. 10);
24663 -- We are asking for a maximum of 10 stack frames.
24665 -- Len will receive the actual number of stack frames returned.
24667 Call_Chain (TB, Len);
24669 Text_IO.Put ("In STB.P1 : ");
24671 for K in 1 .. Len loop
24672 Text_IO.Put (Debug_Utilities.Image (TB (K)));
24693 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
24694 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
24698 You can then get further information by invoking the @code{addr2line}
24699 tool as described earlier (note that the hexadecimal addresses
24700 need to be specified in C format, with a leading ``0x'').
24702 @node Symbolic Traceback
24703 @subsection Symbolic Traceback
24704 @cindex traceback, symbolic
24707 A symbolic traceback is a stack traceback in which procedure names are
24708 associated with each code location.
24711 Note that this feature is not supported on all platforms. See
24712 @file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete
24713 list of currently supported platforms.
24716 Note that the symbolic traceback requires that the program be compiled
24717 with debug information. If it is not compiled with debug information
24718 only the non-symbolic information will be valid.
24721 * Tracebacks From Exception Occurrences (symbolic)::
24722 * Tracebacks From Anywhere in a Program (symbolic)::
24725 @node Tracebacks From Exception Occurrences (symbolic)
24726 @subsubsection Tracebacks From Exception Occurrences
24728 @smallexample @c ada
24730 with GNAT.Traceback.Symbolic;
24736 raise Constraint_Error;
24753 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
24758 $ gnatmake -g .\stb -bargs -E -largs -lgnat -laddr2line -lintl
24761 0040149F in stb.p1 at stb.adb:8
24762 004014B7 in stb.p2 at stb.adb:13
24763 004014CF in stb.p3 at stb.adb:18
24764 004015DD in ada.stb at stb.adb:22
24765 00401461 in main at b~stb.adb:168
24766 004011C4 in __mingw_CRTStartup at crt1.c:200
24767 004011F1 in mainCRTStartup at crt1.c:222
24768 77E892A4 in ?? at ??:0
24772 In the above example the ``.\'' syntax in the @command{gnatmake} command
24773 is currently required by @command{addr2line} for files that are in
24774 the current working directory.
24775 Moreover, the exact sequence of linker options may vary from platform
24777 The above @option{-largs} section is for Windows platforms. By contrast,
24778 under Unix there is no need for the @option{-largs} section.
24779 Differences across platforms are due to details of linker implementation.
24781 @node Tracebacks From Anywhere in a Program (symbolic)
24782 @subsubsection Tracebacks From Anywhere in a Program
24785 It is possible to get a symbolic stack traceback
24786 from anywhere in a program, just as for non-symbolic tracebacks.
24787 The first step is to obtain a non-symbolic
24788 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
24789 information. Here is an example:
24791 @smallexample @c ada
24793 with GNAT.Traceback;
24794 with GNAT.Traceback.Symbolic;
24799 use GNAT.Traceback;
24800 use GNAT.Traceback.Symbolic;
24803 TB : Tracebacks_Array (1 .. 10);
24804 -- We are asking for a maximum of 10 stack frames.
24806 -- Len will receive the actual number of stack frames returned.
24808 Call_Chain (TB, Len);
24809 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
24822 @c ******************************
24824 @node Compatibility with HP Ada
24825 @chapter Compatibility with HP Ada
24826 @cindex Compatibility
24831 @cindex Compatibility between GNAT and HP Ada
24832 This chapter compares HP Ada (formerly known as ``DEC Ada'')
24833 for OpenVMS Alpha and GNAT for OpenVMS for Alpha and for I64.
24834 GNAT is highly compatible
24835 with HP Ada, and it should generally be straightforward to port code
24836 from the HP Ada environment to GNAT. However, there are a few language
24837 and implementation differences of which the user must be aware. These
24838 differences are discussed in this chapter. In
24839 addition, the operating environment and command structure for the
24840 compiler are different, and these differences are also discussed.
24842 For further details on these and other compatibility issues,
24843 see Appendix E of the HP publication
24844 @cite{HP Ada, Technical Overview and Comparison on HP Platforms}.
24846 Except where otherwise indicated, the description of GNAT for OpenVMS
24847 applies to both the Alpha and I64 platforms.
24849 For information on porting Ada code from GNAT on Alpha OpenVMS to GNAT on
24850 I64 OpenVMS, see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
24852 The discussion in this chapter addresses specifically the implementation
24853 of Ada 83 for HP OpenVMS Alpha Systems. In cases where the implementation
24854 of HP Ada differs between OpenVMS Alpha Systems and OpenVMS VAX Systems,
24855 GNAT always follows the Alpha implementation.
24857 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
24858 attributes are recognized, although only a subset of them can sensibly
24859 be implemented. The description of pragmas in
24860 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
24861 indicates whether or not they are applicable to non-VMS systems.
24864 * Ada Language Compatibility::
24865 * Differences in the Definition of Package System::
24866 * Language-Related Features::
24867 * The Package STANDARD::
24868 * The Package SYSTEM::
24869 * Tasking and Task-Related Features::
24870 * Pragmas and Pragma-Related Features::
24871 * Library of Predefined Units::
24873 * Main Program Definition::
24874 * Implementation-Defined Attributes::
24875 * Compiler and Run-Time Interfacing::
24876 * Program Compilation and Library Management::
24878 * Implementation Limits::
24879 * Tools and Utilities::
24882 @node Ada Language Compatibility
24883 @section Ada Language Compatibility
24886 GNAT handles Ada 95 and Ada 2005 as well as Ada 83, whereas HP Ada is only
24887 for Ada 83. Ada 95 and Ada 2005 are almost completely upwards compatible
24888 with Ada 83, and therefore Ada 83 programs will compile
24889 and run under GNAT with
24890 no changes or only minor changes. The @cite{Annotated Ada Reference Manual}
24891 provides details on specific incompatibilities.
24893 GNAT provides the switch @option{/83} on the @command{GNAT COMPILE} command,
24894 as well as the pragma @code{ADA_83}, to force the compiler to
24895 operate in Ada 83 mode. This mode does not guarantee complete
24896 conformance to Ada 83, but in practice is sufficient to
24897 eliminate most sources of incompatibilities.
24898 In particular, it eliminates the recognition of the
24899 additional Ada 95 and Ada 2005 keywords, so that their use as identifiers
24900 in Ada 83 programs is legal, and handles the cases of packages
24901 with optional bodies, and generics that instantiate unconstrained
24902 types without the use of @code{(<>)}.
24904 @node Differences in the Definition of Package System
24905 @section Differences in the Definition of Package @code{System}
24908 An Ada compiler is allowed to add
24909 implementation-dependent declarations to package @code{System}.
24911 GNAT does not take advantage of this permission, and the version of
24912 @code{System} provided by GNAT exactly matches that defined in the Ada
24915 However, HP Ada adds an extensive set of declarations to package
24917 as fully documented in the HP Ada manuals. To minimize changes required
24918 for programs that make use of these extensions, GNAT provides the pragma
24919 @code{Extend_System} for extending the definition of package System. By using:
24920 @cindex pragma @code{Extend_System}
24921 @cindex @code{Extend_System} pragma
24923 @smallexample @c ada
24926 pragma Extend_System (Aux_DEC);
24932 the set of definitions in @code{System} is extended to include those in
24933 package @code{System.Aux_DEC}.
24934 @cindex @code{System.Aux_DEC} package
24935 @cindex @code{Aux_DEC} package (child of @code{System})
24936 These definitions are incorporated directly into package @code{System},
24937 as though they had been declared there. For a
24938 list of the declarations added, see the spec of this package,
24939 which can be found in the file @file{s-auxdec.ads} in the GNAT library.
24940 @cindex @file{s-auxdec.ads} file
24941 The pragma @code{Extend_System} is a configuration pragma, which means that
24942 it can be placed in the file @file{gnat.adc}, so that it will automatically
24943 apply to all subsequent compilations. See @ref{Configuration Pragmas},
24944 for further details.
24946 An alternative approach that avoids the use of the non-standard
24947 @code{Extend_System} pragma is to add a context clause to the unit that
24948 references these facilities:
24950 @smallexample @c ada
24952 with System.Aux_DEC;
24953 use System.Aux_DEC;
24958 The effect is not quite semantically identical to incorporating
24959 the declarations directly into package @code{System},
24960 but most programs will not notice a difference
24961 unless they use prefix notation (e.g.@: @code{System.Integer_8})
24962 to reference the entities directly in package @code{System}.
24963 For units containing such references,
24964 the prefixes must either be removed, or the pragma @code{Extend_System}
24967 @node Language-Related Features
24968 @section Language-Related Features
24971 The following sections highlight differences in types,
24972 representations of types, operations, alignment, and
24976 * Integer Types and Representations::
24977 * Floating-Point Types and Representations::
24978 * Pragmas Float_Representation and Long_Float::
24979 * Fixed-Point Types and Representations::
24980 * Record and Array Component Alignment::
24981 * Address Clauses::
24982 * Other Representation Clauses::
24985 @node Integer Types and Representations
24986 @subsection Integer Types and Representations
24989 The set of predefined integer types is identical in HP Ada and GNAT.
24990 Furthermore the representation of these integer types is also identical,
24991 including the capability of size clauses forcing biased representation.
24994 HP Ada for OpenVMS Alpha systems has defined the
24995 following additional integer types in package @code{System}:
25012 @code{LARGEST_INTEGER}
25016 In GNAT, the first four of these types may be obtained from the
25017 standard Ada package @code{Interfaces}.
25018 Alternatively, by use of the pragma @code{Extend_System}, identical
25019 declarations can be referenced directly in package @code{System}.
25020 On both GNAT and HP Ada, the maximum integer size is 64 bits.
25022 @node Floating-Point Types and Representations
25023 @subsection Floating-Point Types and Representations
25024 @cindex Floating-Point types
25027 The set of predefined floating-point types is identical in HP Ada and GNAT.
25028 Furthermore the representation of these floating-point
25029 types is also identical. One important difference is that the default
25030 representation for HP Ada is @code{VAX_Float}, but the default representation
25033 Specific types may be declared to be @code{VAX_Float} or IEEE, using the
25034 pragma @code{Float_Representation} as described in the HP Ada
25036 For example, the declarations:
25038 @smallexample @c ada
25040 type F_Float is digits 6;
25041 pragma Float_Representation (VAX_Float, F_Float);
25046 declares a type @code{F_Float} that will be represented in @code{VAX_Float}
25048 This set of declarations actually appears in @code{System.Aux_DEC},
25050 the full set of additional floating-point declarations provided in
25051 the HP Ada version of package @code{System}.
25052 This and similar declarations may be accessed in a user program
25053 by using pragma @code{Extend_System}. The use of this
25054 pragma, and the related pragma @code{Long_Float} is described in further
25055 detail in the following section.
25057 @node Pragmas Float_Representation and Long_Float
25058 @subsection Pragmas @code{Float_Representation} and @code{Long_Float}
25061 HP Ada provides the pragma @code{Float_Representation}, which
25062 acts as a program library switch to allow control over
25063 the internal representation chosen for the predefined
25064 floating-point types declared in the package @code{Standard}.
25065 The format of this pragma is as follows:
25067 @smallexample @c ada
25069 pragma Float_Representation(VAX_Float | IEEE_Float);
25074 This pragma controls the representation of floating-point
25079 @code{VAX_Float} specifies that floating-point
25080 types are represented by default with the VAX system hardware types
25081 @code{F-floating}, @code{D-floating}, @code{G-floating}.
25082 Note that the @code{H-floating}
25083 type was available only on VAX systems, and is not available
25084 in either HP Ada or GNAT.
25087 @code{IEEE_Float} specifies that floating-point
25088 types are represented by default with the IEEE single and
25089 double floating-point types.
25093 GNAT provides an identical implementation of the pragma
25094 @code{Float_Representation}, except that it functions as a
25095 configuration pragma. Note that the
25096 notion of configuration pragma corresponds closely to the
25097 HP Ada notion of a program library switch.
25099 When no pragma is used in GNAT, the default is @code{IEEE_Float},
25101 from HP Ada 83, where the default is @code{VAX_Float}. In addition, the
25102 predefined libraries in GNAT are built using @code{IEEE_Float}, so it is not
25103 advisable to change the format of numbers passed to standard library
25104 routines, and if necessary explicit type conversions may be needed.
25106 The use of @code{IEEE_Float} is recommended in GNAT since it is more
25107 efficient, and (given that it conforms to an international standard)
25108 potentially more portable.
25109 The situation in which @code{VAX_Float} may be useful is in interfacing
25110 to existing code and data that expect the use of @code{VAX_Float}.
25111 In such a situation use the predefined @code{VAX_Float}
25112 types in package @code{System}, as extended by
25113 @code{Extend_System}. For example, use @code{System.F_Float}
25114 to specify the 32-bit @code{F-Float} format.
25117 On OpenVMS systems, HP Ada provides the pragma @code{Long_Float}
25118 to allow control over the internal representation chosen
25119 for the predefined type @code{Long_Float} and for floating-point
25120 type declarations with digits specified in the range 7 .. 15.
25121 The format of this pragma is as follows:
25123 @smallexample @c ada
25125 pragma Long_Float (D_FLOAT | G_FLOAT);
25129 @node Fixed-Point Types and Representations
25130 @subsection Fixed-Point Types and Representations
25133 On HP Ada for OpenVMS Alpha systems, rounding is
25134 away from zero for both positive and negative numbers.
25135 Therefore, @code{+0.5} rounds to @code{1},
25136 and @code{-0.5} rounds to @code{-1}.
25138 On GNAT the results of operations
25139 on fixed-point types are in accordance with the Ada
25140 rules. In particular, results of operations on decimal
25141 fixed-point types are truncated.
25143 @node Record and Array Component Alignment
25144 @subsection Record and Array Component Alignment
25147 On HP Ada for OpenVMS Alpha, all non-composite components
25148 are aligned on natural boundaries. For example, 1-byte
25149 components are aligned on byte boundaries, 2-byte
25150 components on 2-byte boundaries, 4-byte components on 4-byte
25151 byte boundaries, and so on. The OpenVMS Alpha hardware
25152 runs more efficiently with naturally aligned data.
25154 On GNAT, alignment rules are compatible
25155 with HP Ada for OpenVMS Alpha.
25157 @node Address Clauses
25158 @subsection Address Clauses
25161 In HP Ada and GNAT, address clauses are supported for
25162 objects and imported subprograms.
25163 The predefined type @code{System.Address} is a private type
25164 in both compilers on Alpha OpenVMS, with the same representation
25165 (it is simply a machine pointer). Addition, subtraction, and comparison
25166 operations are available in the standard Ada package
25167 @code{System.Storage_Elements}, or in package @code{System}
25168 if it is extended to include @code{System.Aux_DEC} using a
25169 pragma @code{Extend_System} as previously described.
25171 Note that code that @code{with}'s both this extended package @code{System}
25172 and the package @code{System.Storage_Elements} should not @code{use}
25173 both packages, or ambiguities will result. In general it is better
25174 not to mix these two sets of facilities. The Ada package was
25175 designed specifically to provide the kind of features that HP Ada
25176 adds directly to package @code{System}.
25178 The type @code{System.Address} is a 64-bit integer type in GNAT for
25179 I64 OpenVMS. For more information,
25180 see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
25182 GNAT is compatible with HP Ada in its handling of address
25183 clauses, except for some limitations in
25184 the form of address clauses for composite objects with
25185 initialization. Such address clauses are easily replaced
25186 by the use of an explicitly-defined constant as described
25187 in the Ada Reference Manual (13.1(22)). For example, the sequence
25190 @smallexample @c ada
25192 X, Y : Integer := Init_Func;
25193 Q : String (X .. Y) := "abc";
25195 for Q'Address use Compute_Address;
25200 will be rejected by GNAT, since the address cannot be computed at the time
25201 that @code{Q} is declared. To achieve the intended effect, write instead:
25203 @smallexample @c ada
25206 X, Y : Integer := Init_Func;
25207 Q_Address : constant Address := Compute_Address;
25208 Q : String (X .. Y) := "abc";
25210 for Q'Address use Q_Address;
25216 which will be accepted by GNAT (and other Ada compilers), and is also
25217 compatible with Ada 83. A fuller description of the restrictions
25218 on address specifications is found in @ref{Top, GNAT Reference Manual,
25219 About This Guide, gnat_rm, GNAT Reference Manual}.
25221 @node Other Representation Clauses
25222 @subsection Other Representation Clauses
25225 GNAT implements in a compatible manner all the representation
25226 clauses supported by HP Ada. In addition, GNAT
25227 implements the representation clause forms that were introduced in Ada 95,
25228 including @code{COMPONENT_SIZE} and @code{SIZE} clauses for objects.
25230 @node The Package STANDARD
25231 @section The Package @code{STANDARD}
25234 The package @code{STANDARD}, as implemented by HP Ada, is fully
25235 described in the @cite{Ada Reference Manual} and in the
25236 @cite{HP Ada Language Reference Manual}. As implemented by GNAT, the
25237 package @code{STANDARD} is described in the @cite{Ada Reference Manual}.
25239 In addition, HP Ada supports the Latin-1 character set in
25240 the type @code{CHARACTER}. GNAT supports the Latin-1 character set
25241 in the type @code{CHARACTER} and also Unicode (ISO 10646 BMP) in
25242 the type @code{WIDE_CHARACTER}.
25244 The floating-point types supported by GNAT are those
25245 supported by HP Ada, but the defaults are different, and are controlled by
25246 pragmas. See @ref{Floating-Point Types and Representations}, for details.
25248 @node The Package SYSTEM
25249 @section The Package @code{SYSTEM}
25252 HP Ada provides a specific version of the package
25253 @code{SYSTEM} for each platform on which the language is implemented.
25254 For the complete spec of the package @code{SYSTEM}, see
25255 Appendix F of the @cite{HP Ada Language Reference Manual}.
25257 On HP Ada, the package @code{SYSTEM} includes the following conversion
25260 @item @code{TO_ADDRESS(INTEGER)}
25262 @item @code{TO_ADDRESS(UNSIGNED_LONGWORD)}
25264 @item @code{TO_ADDRESS(}@i{universal_integer}@code{)}
25266 @item @code{TO_INTEGER(ADDRESS)}
25268 @item @code{TO_UNSIGNED_LONGWORD(ADDRESS)}
25270 @item Function @code{IMPORT_VALUE return UNSIGNED_LONGWORD} and the
25271 functions @code{IMPORT_ADDRESS} and @code{IMPORT_LARGEST_VALUE}
25275 By default, GNAT supplies a version of @code{SYSTEM} that matches
25276 the definition given in the @cite{Ada Reference Manual}.
25278 is a subset of the HP system definitions, which is as
25279 close as possible to the original definitions. The only difference
25280 is that the definition of @code{SYSTEM_NAME} is different:
25282 @smallexample @c ada
25284 type Name is (SYSTEM_NAME_GNAT);
25285 System_Name : constant Name := SYSTEM_NAME_GNAT;
25290 Also, GNAT adds the Ada declarations for
25291 @code{BIT_ORDER} and @code{DEFAULT_BIT_ORDER}.
25293 However, the use of the following pragma causes GNAT
25294 to extend the definition of package @code{SYSTEM} so that it
25295 encompasses the full set of HP-specific extensions,
25296 including the functions listed above:
25298 @smallexample @c ada
25300 pragma Extend_System (Aux_DEC);
25305 The pragma @code{Extend_System} is a configuration pragma that
25306 is most conveniently placed in the @file{gnat.adc} file. @xref{Pragma
25307 Extend_System,,, gnat_rm, GNAT Reference Manual} for further details.
25309 HP Ada does not allow the recompilation of the package
25310 @code{SYSTEM}. Instead HP Ada provides several pragmas
25311 (@code{SYSTEM_NAME}, @code{STORAGE_UNIT}, and @code{MEMORY_SIZE})
25312 to modify values in the package @code{SYSTEM}.
25313 On OpenVMS Alpha systems, the pragma
25314 @code{SYSTEM_NAME} takes the enumeration literal @code{OPENVMS_AXP} as
25315 its single argument.
25317 GNAT does permit the recompilation of package @code{SYSTEM} using
25318 the special switch @option{-gnatg}, and this switch can be used if
25319 it is necessary to modify the definitions in @code{SYSTEM}. GNAT does
25320 not permit the specification of @code{SYSTEM_NAME}, @code{STORAGE_UNIT}
25321 or @code{MEMORY_SIZE} by any other means.
25323 On GNAT systems, the pragma @code{SYSTEM_NAME} takes the
25324 enumeration literal @code{SYSTEM_NAME_GNAT}.
25326 The definitions provided by the use of
25328 @smallexample @c ada
25329 pragma Extend_System (AUX_Dec);
25333 are virtually identical to those provided by the HP Ada 83 package
25334 @code{SYSTEM}. One important difference is that the name of the
25336 function for type @code{UNSIGNED_LONGWORD} is changed to
25337 @code{TO_ADDRESS_LONG}.
25338 @xref{Address Clauses,,, gnat_rm, GNAT Reference Manual} for a
25339 discussion of why this change was necessary.
25342 The version of @code{TO_ADDRESS} taking a @i{universal_integer} argument
25344 an extension to Ada 83 not strictly compatible with the reference manual.
25345 GNAT, in order to be exactly compatible with the standard,
25346 does not provide this capability. In HP Ada 83, the
25347 point of this definition is to deal with a call like:
25349 @smallexample @c ada
25350 TO_ADDRESS (16#12777#);
25354 Normally, according to Ada 83 semantics, one would expect this to be
25355 ambiguous, since it matches both the @code{INTEGER} and
25356 @code{UNSIGNED_LONGWORD} forms of @code{TO_ADDRESS}.
25357 However, in HP Ada 83, there is no ambiguity, since the
25358 definition using @i{universal_integer} takes precedence.
25360 In GNAT, since the version with @i{universal_integer} cannot be supplied,
25362 not possible to be 100% compatible. Since there are many programs using
25363 numeric constants for the argument to @code{TO_ADDRESS}, the decision in
25365 to change the name of the function in the @code{UNSIGNED_LONGWORD} case,
25366 so the declarations provided in the GNAT version of @code{AUX_Dec} are:
25368 @smallexample @c ada
25369 function To_Address (X : Integer) return Address;
25370 pragma Pure_Function (To_Address);
25372 function To_Address_Long (X : Unsigned_Longword) return Address;
25373 pragma Pure_Function (To_Address_Long);
25377 This means that programs using @code{TO_ADDRESS} for
25378 @code{UNSIGNED_LONGWORD} must change the name to @code{TO_ADDRESS_LONG}.
25380 @node Tasking and Task-Related Features
25381 @section Tasking and Task-Related Features
25384 This section compares the treatment of tasking in GNAT
25385 and in HP Ada for OpenVMS Alpha.
25386 The GNAT description applies to both Alpha and I64 OpenVMS.
25387 For detailed information on tasking in
25388 HP Ada, see the @cite{HP Ada Language Reference Manual} and the
25389 relevant run-time reference manual.
25392 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
25393 * Assigning Task IDs::
25394 * Task IDs and Delays::
25395 * Task-Related Pragmas::
25396 * Scheduling and Task Priority::
25398 * External Interrupts::
25401 @node Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
25402 @subsection Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
25405 On OpenVMS Alpha systems, each Ada task (except a passive
25406 task) is implemented as a single stream of execution
25407 that is created and managed by the kernel. On these
25408 systems, HP Ada tasking support is based on DECthreads,
25409 an implementation of the POSIX standard for threads.
25411 Also, on OpenVMS Alpha systems, HP Ada tasks and foreign
25412 code that calls DECthreads routines can be used together.
25413 The interaction between Ada tasks and DECthreads routines
25414 can have some benefits. For example when on OpenVMS Alpha,
25415 HP Ada can call C code that is already threaded.
25417 GNAT uses the facilities of DECthreads,
25418 and Ada tasks are mapped to threads.
25420 @node Assigning Task IDs
25421 @subsection Assigning Task IDs
25424 The HP Ada Run-Time Library always assigns @code{%TASK 1} to
25425 the environment task that executes the main program. On
25426 OpenVMS Alpha systems, @code{%TASK 0} is often used for tasks
25427 that have been created but are not yet activated.
25429 On OpenVMS Alpha systems, task IDs are assigned at
25430 activation. On GNAT systems, task IDs are also assigned at
25431 task creation but do not have the same form or values as
25432 task ID values in HP Ada. There is no null task, and the
25433 environment task does not have a specific task ID value.
25435 @node Task IDs and Delays
25436 @subsection Task IDs and Delays
25439 On OpenVMS Alpha systems, tasking delays are implemented
25440 using Timer System Services. The Task ID is used for the
25441 identification of the timer request (the @code{REQIDT} parameter).
25442 If Timers are used in the application take care not to use
25443 @code{0} for the identification, because cancelling such a timer
25444 will cancel all timers and may lead to unpredictable results.
25446 @node Task-Related Pragmas
25447 @subsection Task-Related Pragmas
25450 Ada supplies the pragma @code{TASK_STORAGE}, which allows
25451 specification of the size of the guard area for a task
25452 stack. (The guard area forms an area of memory that has no
25453 read or write access and thus helps in the detection of
25454 stack overflow.) On OpenVMS Alpha systems, if the pragma
25455 @code{TASK_STORAGE} specifies a value of zero, a minimal guard
25456 area is created. In the absence of a pragma @code{TASK_STORAGE},
25457 a default guard area is created.
25459 GNAT supplies the following task-related pragmas:
25462 @item @code{TASK_INFO}
25464 This pragma appears within a task definition and
25465 applies to the task in which it appears. The argument
25466 must be of type @code{SYSTEM.TASK_INFO.TASK_INFO_TYPE}.
25468 @item @code{TASK_STORAGE}
25470 GNAT implements pragma @code{TASK_STORAGE} in the same way as HP Ada.
25471 Both HP Ada and GNAT supply the pragmas @code{PASSIVE},
25472 @code{SUPPRESS}, and @code{VOLATILE}.
25474 @node Scheduling and Task Priority
25475 @subsection Scheduling and Task Priority
25478 HP Ada implements the Ada language requirement that
25479 when two tasks are eligible for execution and they have
25480 different priorities, the lower priority task does not
25481 execute while the higher priority task is waiting. The HP
25482 Ada Run-Time Library keeps a task running until either the
25483 task is suspended or a higher priority task becomes ready.
25485 On OpenVMS Alpha systems, the default strategy is round-
25486 robin with preemption. Tasks of equal priority take turns
25487 at the processor. A task is run for a certain period of
25488 time and then placed at the tail of the ready queue for
25489 its priority level.
25491 HP Ada provides the implementation-defined pragma @code{TIME_SLICE},
25492 which can be used to enable or disable round-robin
25493 scheduling of tasks with the same priority.
25494 See the relevant HP Ada run-time reference manual for
25495 information on using the pragmas to control HP Ada task
25498 GNAT follows the scheduling rules of Annex D (Real-Time
25499 Annex) of the @cite{Ada Reference Manual}. In general, this
25500 scheduling strategy is fully compatible with HP Ada
25501 although it provides some additional constraints (as
25502 fully documented in Annex D).
25503 GNAT implements time slicing control in a manner compatible with
25504 HP Ada 83, by means of the pragma @code{Time_Slice}, whose semantics
25505 are identical to the HP Ada 83 pragma of the same name.
25506 Note that it is not possible to mix GNAT tasking and
25507 HP Ada 83 tasking in the same program, since the two run-time
25508 libraries are not compatible.
25510 @node The Task Stack
25511 @subsection The Task Stack
25514 In HP Ada, a task stack is allocated each time a
25515 non-passive task is activated. As soon as the task is
25516 terminated, the storage for the task stack is deallocated.
25517 If you specify a size of zero (bytes) with @code{T'STORAGE_SIZE},
25518 a default stack size is used. Also, regardless of the size
25519 specified, some additional space is allocated for task
25520 management purposes. On OpenVMS Alpha systems, at least
25521 one page is allocated.
25523 GNAT handles task stacks in a similar manner. In accordance with
25524 the Ada rules, it provides the pragma @code{STORAGE_SIZE} as
25525 an alternative method for controlling the task stack size.
25526 The specification of the attribute @code{T'STORAGE_SIZE} is also
25527 supported in a manner compatible with HP Ada.
25529 @node External Interrupts
25530 @subsection External Interrupts
25533 On HP Ada, external interrupts can be associated with task entries.
25534 GNAT is compatible with HP Ada in its handling of external interrupts.
25536 @node Pragmas and Pragma-Related Features
25537 @section Pragmas and Pragma-Related Features
25540 Both HP Ada and GNAT supply all language-defined pragmas
25541 as specified by the Ada 83 standard. GNAT also supplies all
25542 language-defined pragmas introduced by Ada 95 and Ada 2005.
25543 In addition, GNAT implements the implementation-defined pragmas
25547 @item @code{AST_ENTRY}
25549 @item @code{COMMON_OBJECT}
25551 @item @code{COMPONENT_ALIGNMENT}
25553 @item @code{EXPORT_EXCEPTION}
25555 @item @code{EXPORT_FUNCTION}
25557 @item @code{EXPORT_OBJECT}
25559 @item @code{EXPORT_PROCEDURE}
25561 @item @code{EXPORT_VALUED_PROCEDURE}
25563 @item @code{FLOAT_REPRESENTATION}
25567 @item @code{IMPORT_EXCEPTION}
25569 @item @code{IMPORT_FUNCTION}
25571 @item @code{IMPORT_OBJECT}
25573 @item @code{IMPORT_PROCEDURE}
25575 @item @code{IMPORT_VALUED_PROCEDURE}
25577 @item @code{INLINE_GENERIC}
25579 @item @code{INTERFACE_NAME}
25581 @item @code{LONG_FLOAT}
25583 @item @code{MAIN_STORAGE}
25585 @item @code{PASSIVE}
25587 @item @code{PSECT_OBJECT}
25589 @item @code{SHARE_GENERIC}
25591 @item @code{SUPPRESS_ALL}
25593 @item @code{TASK_STORAGE}
25595 @item @code{TIME_SLICE}
25601 These pragmas are all fully implemented, with the exception of @code{TITLE},
25602 @code{PASSIVE}, and @code{SHARE_GENERIC}, which are
25603 recognized, but which have no
25604 effect in GNAT. The effect of @code{PASSIVE} may be obtained by the
25605 use of Ada protected objects. In GNAT, all generics are inlined.
25607 Unlike HP Ada, the GNAT ``@code{EXPORT_}@i{subprogram}'' pragmas require
25608 a separate subprogram specification which must appear before the
25611 GNAT also supplies a number of implementation-defined pragmas as follows:
25613 @item @code{ABORT_DEFER}
25615 @item @code{ADA_83}
25617 @item @code{ADA_95}
25619 @item @code{ADA_05}
25621 @item @code{ANNOTATE}
25623 @item @code{ASSERT}
25625 @item @code{C_PASS_BY_COPY}
25627 @item @code{CPP_CLASS}
25629 @item @code{CPP_CONSTRUCTOR}
25631 @item @code{CPP_DESTRUCTOR}
25635 @item @code{EXTEND_SYSTEM}
25637 @item @code{LINKER_ALIAS}
25639 @item @code{LINKER_SECTION}
25641 @item @code{MACHINE_ATTRIBUTE}
25643 @item @code{NO_RETURN}
25645 @item @code{PURE_FUNCTION}
25647 @item @code{SOURCE_FILE_NAME}
25649 @item @code{SOURCE_REFERENCE}
25651 @item @code{TASK_INFO}
25653 @item @code{UNCHECKED_UNION}
25655 @item @code{UNIMPLEMENTED_UNIT}
25657 @item @code{UNIVERSAL_DATA}
25659 @item @code{UNSUPPRESS}
25661 @item @code{WARNINGS}
25663 @item @code{WEAK_EXTERNAL}
25667 For full details on these GNAT implementation-defined pragmas,
25668 see @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
25672 * Restrictions on the Pragma INLINE::
25673 * Restrictions on the Pragma INTERFACE::
25674 * Restrictions on the Pragma SYSTEM_NAME::
25677 @node Restrictions on the Pragma INLINE
25678 @subsection Restrictions on Pragma @code{INLINE}
25681 HP Ada enforces the following restrictions on the pragma @code{INLINE}:
25683 @item Parameters cannot have a task type.
25685 @item Function results cannot be task types, unconstrained
25686 array types, or unconstrained types with discriminants.
25688 @item Bodies cannot declare the following:
25690 @item Subprogram body or stub (imported subprogram is allowed)
25694 @item Generic declarations
25696 @item Instantiations
25700 @item Access types (types derived from access types allowed)
25702 @item Array or record types
25704 @item Dependent tasks
25706 @item Direct recursive calls of subprogram or containing
25707 subprogram, directly or via a renaming
25713 In GNAT, the only restriction on pragma @code{INLINE} is that the
25714 body must occur before the call if both are in the same
25715 unit, and the size must be appropriately small. There are
25716 no other specific restrictions which cause subprograms to
25717 be incapable of being inlined.
25719 @node Restrictions on the Pragma INTERFACE
25720 @subsection Restrictions on Pragma @code{INTERFACE}
25723 The following restrictions on pragma @code{INTERFACE}
25724 are enforced by both HP Ada and GNAT:
25726 @item Languages accepted: Ada, Bliss, C, Fortran, Default.
25727 Default is the default on OpenVMS Alpha systems.
25729 @item Parameter passing: Language specifies default
25730 mechanisms but can be overridden with an @code{EXPORT} pragma.
25733 @item Ada: Use internal Ada rules.
25735 @item Bliss, C: Parameters must be mode @code{in}; cannot be
25736 record or task type. Result cannot be a string, an
25737 array, or a record.
25739 @item Fortran: Parameters cannot have a task type. Result cannot
25740 be a string, an array, or a record.
25745 GNAT is entirely upwards compatible with HP Ada, and in addition allows
25746 record parameters for all languages.
25748 @node Restrictions on the Pragma SYSTEM_NAME
25749 @subsection Restrictions on Pragma @code{SYSTEM_NAME}
25752 For HP Ada for OpenVMS Alpha, the enumeration literal
25753 for the type @code{NAME} is @code{OPENVMS_AXP}.
25754 In GNAT, the enumeration
25755 literal for the type @code{NAME} is @code{SYSTEM_NAME_GNAT}.
25757 @node Library of Predefined Units
25758 @section Library of Predefined Units
25761 A library of predefined units is provided as part of the
25762 HP Ada and GNAT implementations. HP Ada does not provide
25763 the package @code{MACHINE_CODE} but instead recommends importing
25766 The GNAT versions of the HP Ada Run-Time Library (@code{ADA$PREDEFINED:})
25767 units are taken from the OpenVMS Alpha version, not the OpenVMS VAX
25769 The HP Ada Predefined Library units are modified to remove post-Ada 83
25770 incompatibilities and to make them interoperable with GNAT
25771 (@pxref{Changes to DECLIB}, for details).
25772 The units are located in the @file{DECLIB} directory.
25774 The GNAT RTL is contained in
25775 the @file{ADALIB} directory, and
25776 the default search path is set up to find @code{DECLIB} units in preference
25777 to @code{ADALIB} units with the same name (@code{TEXT_IO},
25778 @code{SEQUENTIAL_IO}, and @code{DIRECT_IO}, for example).
25781 * Changes to DECLIB::
25784 @node Changes to DECLIB
25785 @subsection Changes to @code{DECLIB}
25788 The changes made to the HP Ada predefined library for GNAT and post-Ada 83
25789 compatibility are minor and include the following:
25792 @item Adjusting the location of pragmas and record representation
25793 clauses to obey Ada 95 (and thus Ada 2005) rules
25795 @item Adding the proper notation to generic formal parameters
25796 that take unconstrained types in instantiation
25798 @item Adding pragma @code{ELABORATE_BODY} to package specs
25799 that have package bodies not otherwise allowed
25801 @item Replacing occurrences of the identifier ``@code{PROTECTED}'' by
25802 ``@code{PROTECTD}''.
25803 Currently these are found only in the @code{STARLET} package spec.
25805 @item Changing @code{SYSTEM.ADDRESS} to @code{SYSTEM.SHORT_ADDRESS}
25806 where the address size is constrained to 32 bits.
25810 None of the above changes is visible to users.
25816 On OpenVMS Alpha, HP Ada provides the following strongly-typed bindings:
25819 @item Command Language Interpreter (CLI interface)
25821 @item DECtalk Run-Time Library (DTK interface)
25823 @item Librarian utility routines (LBR interface)
25825 @item General Purpose Run-Time Library (LIB interface)
25827 @item Math Run-Time Library (MTH interface)
25829 @item National Character Set Run-Time Library (NCS interface)
25831 @item Compiled Code Support Run-Time Library (OTS interface)
25833 @item Parallel Processing Run-Time Library (PPL interface)
25835 @item Screen Management Run-Time Library (SMG interface)
25837 @item Sort Run-Time Library (SOR interface)
25839 @item String Run-Time Library (STR interface)
25841 @item STARLET System Library
25844 @item X Window System Version 11R4 and 11R5 (X, XLIB interface)
25846 @item X Windows Toolkit (XT interface)
25848 @item X/Motif Version 1.1.3 and 1.2 (XM interface)
25852 GNAT provides implementations of these HP bindings in the @code{DECLIB}
25853 directory, on both the Alpha and I64 OpenVMS platforms.
25855 The X/Motif bindings used to build @code{DECLIB} are whatever versions are
25857 HP Ada @file{ADA$PREDEFINED} directory with extension @file{.ADC}.
25858 A pragma @code{Linker_Options} has been added to packages @code{Xm},
25859 @code{Xt}, and @code{X_Lib}
25860 causing the default X/Motif sharable image libraries to be linked in. This
25861 is done via options files named @file{xm.opt}, @file{xt.opt}, and
25862 @file{x_lib.opt} (also located in the @file{DECLIB} directory).
25864 It may be necessary to edit these options files to update or correct the
25865 library names if, for example, the newer X/Motif bindings from
25866 @file{ADA$EXAMPLES}
25867 had been (previous to installing GNAT) copied and renamed to supersede the
25868 default @file{ADA$PREDEFINED} versions.
25871 * Shared Libraries and Options Files::
25872 * Interfaces to C::
25875 @node Shared Libraries and Options Files
25876 @subsection Shared Libraries and Options Files
25879 When using the HP Ada
25880 predefined X and Motif bindings, the linking with their sharable images is
25881 done automatically by @command{GNAT LINK}.
25882 When using other X and Motif bindings, you need
25883 to add the corresponding sharable images to the command line for
25884 @code{GNAT LINK}. When linking with shared libraries, or with
25885 @file{.OPT} files, you must
25886 also add them to the command line for @command{GNAT LINK}.
25888 A shared library to be used with GNAT is built in the same way as other
25889 libraries under VMS. The VMS Link command can be used in standard fashion.
25891 @node Interfaces to C
25892 @subsection Interfaces to C
25896 provides the following Ada types and operations:
25899 @item C types package (@code{C_TYPES})
25901 @item C strings (@code{C_TYPES.NULL_TERMINATED})
25903 @item Other_types (@code{SHORT_INT})
25907 Interfacing to C with GNAT, you can use the above approach
25908 described for HP Ada or the facilities of Annex B of
25909 the @cite{Ada Reference Manual} (packages @code{INTERFACES.C},
25910 @code{INTERFACES.C.STRINGS} and @code{INTERFACES.C.POINTERS}). For more
25911 information, see @ref{Interfacing to C,,, gnat_rm, GNAT Reference Manual}.
25913 The @option{-gnatF} qualifier forces default and explicit
25914 @code{External_Name} parameters in pragmas @code{Import} and @code{Export}
25915 to be uppercased for compatibility with the default behavior
25916 of HP C. The qualifier has no effect on @code{Link_Name} parameters.
25918 @node Main Program Definition
25919 @section Main Program Definition
25922 The following section discusses differences in the
25923 definition of main programs on HP Ada and GNAT.
25924 On HP Ada, main programs are defined to meet the
25925 following conditions:
25927 @item Procedure with no formal parameters (returns @code{0} upon
25930 @item Procedure with no formal parameters (returns @code{42} when
25931 an unhandled exception is raised)
25933 @item Function with no formal parameters whose returned value
25934 is of a discrete type
25936 @item Procedure with one @code{out} formal of a discrete type for
25937 which a specification of pragma @code{EXPORT_VALUED_PROCEDURE} is given.
25942 When declared with the pragma @code{EXPORT_VALUED_PROCEDURE},
25943 a main function or main procedure returns a discrete
25944 value whose size is less than 64 bits (32 on VAX systems),
25945 the value is zero- or sign-extended as appropriate.
25946 On GNAT, main programs are defined as follows:
25948 @item Must be a non-generic, parameterless subprogram that
25949 is either a procedure or function returning an Ada
25950 @code{STANDARD.INTEGER} (the predefined type)
25952 @item Cannot be a generic subprogram or an instantiation of a
25956 @node Implementation-Defined Attributes
25957 @section Implementation-Defined Attributes
25960 GNAT provides all HP Ada implementation-defined
25963 @node Compiler and Run-Time Interfacing
25964 @section Compiler and Run-Time Interfacing
25967 HP Ada provides the following qualifiers to pass options to the linker
25970 @item @option{/WAIT} and @option{/SUBMIT}
25972 @item @option{/COMMAND}
25974 @item @option{/@r{[}NO@r{]}MAP}
25976 @item @option{/OUTPUT=@var{file-spec}}
25978 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
25982 To pass options to the linker, GNAT provides the following
25986 @item @option{/EXECUTABLE=@var{exec-name}}
25988 @item @option{/VERBOSE}
25990 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
25994 For more information on these switches, see
25995 @ref{Switches for gnatlink}.
25996 In HP Ada, the command-line switch @option{/OPTIMIZE} is available
25997 to control optimization. HP Ada also supplies the
26000 @item @code{OPTIMIZE}
26002 @item @code{INLINE}
26004 @item @code{INLINE_GENERIC}
26006 @item @code{SUPPRESS_ALL}
26008 @item @code{PASSIVE}
26012 In GNAT, optimization is controlled strictly by command
26013 line parameters, as described in the corresponding section of this guide.
26014 The HP pragmas for control of optimization are
26015 recognized but ignored.
26017 Note that in GNAT, the default is optimization off, whereas in HP Ada
26018 the default is that optimization is turned on.
26020 @node Program Compilation and Library Management
26021 @section Program Compilation and Library Management
26024 HP Ada and GNAT provide a comparable set of commands to
26025 build programs. HP Ada also provides a program library,
26026 which is a concept that does not exist on GNAT. Instead,
26027 GNAT provides directories of sources that are compiled as
26030 The following table summarizes
26031 the HP Ada commands and provides
26032 equivalent GNAT commands. In this table, some GNAT
26033 equivalents reflect the fact that GNAT does not use the
26034 concept of a program library. Instead, it uses a model
26035 in which collections of source and object files are used
26036 in a manner consistent with other languages like C and
26037 Fortran. Therefore, standard system file commands are used
26038 to manipulate these elements. Those GNAT commands are marked with
26040 Note that, unlike HP Ada, none of the GNAT commands accepts wild cards.
26043 @multitable @columnfractions .35 .65
26045 @item @emph{HP Ada Command}
26046 @tab @emph{GNAT Equivalent / Description}
26048 @item @command{ADA}
26049 @tab @command{GNAT COMPILE}@*
26050 Invokes the compiler to compile one or more Ada source files.
26052 @item @command{ACS ATTACH}@*
26053 @tab [No equivalent]@*
26054 Switches control of terminal from current process running the program
26057 @item @command{ACS CHECK}
26058 @tab @command{GNAT MAKE /DEPENDENCY_LIST}@*
26059 Forms the execution closure of one
26060 or more compiled units and checks completeness and currency.
26062 @item @command{ACS COMPILE}
26063 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
26064 Forms the execution closure of one or
26065 more specified units, checks completeness and currency,
26066 identifies units that have revised source files, compiles same,
26067 and recompiles units that are or will become obsolete.
26068 Also completes incomplete generic instantiations.
26070 @item @command{ACS COPY FOREIGN}
26072 Copies a foreign object file into the program library as a
26075 @item @command{ACS COPY UNIT}
26077 Copies a compiled unit from one program library to another.
26079 @item @command{ACS CREATE LIBRARY}
26080 @tab Create /directory (*)@*
26081 Creates a program library.
26083 @item @command{ACS CREATE SUBLIBRARY}
26084 @tab Create /directory (*)@*
26085 Creates a program sublibrary.
26087 @item @command{ACS DELETE LIBRARY}
26089 Deletes a program library and its contents.
26091 @item @command{ACS DELETE SUBLIBRARY}
26093 Deletes a program sublibrary and its contents.
26095 @item @command{ACS DELETE UNIT}
26096 @tab Delete file (*)@*
26097 On OpenVMS systems, deletes one or more compiled units from
26098 the current program library.
26100 @item @command{ACS DIRECTORY}
26101 @tab Directory (*)@*
26102 On OpenVMS systems, lists units contained in the current
26105 @item @command{ACS ENTER FOREIGN}
26107 Allows the import of a foreign body as an Ada library
26108 spec and enters a reference to a pointer.
26110 @item @command{ACS ENTER UNIT}
26112 Enters a reference (pointer) from the current program library to
26113 a unit compiled into another program library.
26115 @item @command{ACS EXIT}
26116 @tab [No equivalent]@*
26117 Exits from the program library manager.
26119 @item @command{ACS EXPORT}
26121 Creates an object file that contains system-specific object code
26122 for one or more units. With GNAT, object files can simply be copied
26123 into the desired directory.
26125 @item @command{ACS EXTRACT SOURCE}
26127 Allows access to the copied source file for each Ada compilation unit
26129 @item @command{ACS HELP}
26130 @tab @command{HELP GNAT}@*
26131 Provides online help.
26133 @item @command{ACS LINK}
26134 @tab @command{GNAT LINK}@*
26135 Links an object file containing Ada units into an executable file.
26137 @item @command{ACS LOAD}
26139 Loads (partially compiles) Ada units into the program library.
26140 Allows loading a program from a collection of files into a library
26141 without knowing the relationship among units.
26143 @item @command{ACS MERGE}
26145 Merges into the current program library, one or more units from
26146 another library where they were modified.
26148 @item @command{ACS RECOMPILE}
26149 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
26150 Recompiles from external or copied source files any obsolete
26151 unit in the closure. Also, completes any incomplete generic
26154 @item @command{ACS REENTER}
26155 @tab @command{GNAT MAKE}@*
26156 Reenters current references to units compiled after last entered
26157 with the @command{ACS ENTER UNIT} command.
26159 @item @command{ACS SET LIBRARY}
26160 @tab Set default (*)@*
26161 Defines a program library to be the compilation context as well
26162 as the target library for compiler output and commands in general.
26164 @item @command{ACS SET PRAGMA}
26165 @tab Edit @file{gnat.adc} (*)@*
26166 Redefines specified values of the library characteristics
26167 @code{LONG_ FLOAT}, @code{MEMORY_SIZE}, @code{SYSTEM_NAME},
26168 and @code{Float_Representation}.
26170 @item @command{ACS SET SOURCE}
26171 @tab Define @code{ADA_INCLUDE_PATH} path (*)@*
26172 Defines the source file search list for the @command{ACS COMPILE} command.
26174 @item @command{ACS SHOW LIBRARY}
26175 @tab Directory (*)@*
26176 Lists information about one or more program libraries.
26178 @item @command{ACS SHOW PROGRAM}
26179 @tab [No equivalent]@*
26180 Lists information about the execution closure of one or
26181 more units in the program library.
26183 @item @command{ACS SHOW SOURCE}
26184 @tab Show logical @code{ADA_INCLUDE_PATH}@*
26185 Shows the source file search used when compiling units.
26187 @item @command{ACS SHOW VERSION}
26188 @tab Compile with @option{VERBOSE} option
26189 Displays the version number of the compiler and program library
26192 @item @command{ACS SPAWN}
26193 @tab [No equivalent]@*
26194 Creates a subprocess of the current process (same as @command{DCL SPAWN}
26197 @item @command{ACS VERIFY}
26198 @tab [No equivalent]@*
26199 Performs a series of consistency checks on a program library to
26200 determine whether the library structure and library files are in
26207 @section Input-Output
26210 On OpenVMS Alpha systems, HP Ada uses OpenVMS Record
26211 Management Services (RMS) to perform operations on
26215 HP Ada and GNAT predefine an identical set of input-
26216 output packages. To make the use of the
26217 generic @code{TEXT_IO} operations more convenient, HP Ada
26218 provides predefined library packages that instantiate the
26219 integer and floating-point operations for the predefined
26220 integer and floating-point types as shown in the following table.
26222 @multitable @columnfractions .45 .55
26223 @item @emph{Package Name} @tab Instantiation
26225 @item @code{INTEGER_TEXT_IO}
26226 @tab @code{INTEGER_IO(INTEGER)}
26228 @item @code{SHORT_INTEGER_TEXT_IO}
26229 @tab @code{INTEGER_IO(SHORT_INTEGER)}
26231 @item @code{SHORT_SHORT_INTEGER_TEXT_IO}
26232 @tab @code{INTEGER_IO(SHORT_SHORT_INTEGER)}
26234 @item @code{FLOAT_TEXT_IO}
26235 @tab @code{FLOAT_IO(FLOAT)}
26237 @item @code{LONG_FLOAT_TEXT_IO}
26238 @tab @code{FLOAT_IO(LONG_FLOAT)}
26242 The HP Ada predefined packages and their operations
26243 are implemented using OpenVMS Alpha files and input-output
26244 facilities. HP Ada supports asynchronous input-output on OpenVMS Alpha.
26245 Familiarity with the following is recommended:
26247 @item RMS file organizations and access methods
26249 @item OpenVMS file specifications and directories
26251 @item OpenVMS File Definition Language (FDL)
26255 GNAT provides I/O facilities that are completely
26256 compatible with HP Ada. The distribution includes the
26257 standard HP Ada versions of all I/O packages, operating
26258 in a manner compatible with HP Ada. In particular, the
26259 following packages are by default the HP Ada (Ada 83)
26260 versions of these packages rather than the renamings
26261 suggested in Annex J of the Ada Reference Manual:
26263 @item @code{TEXT_IO}
26265 @item @code{SEQUENTIAL_IO}
26267 @item @code{DIRECT_IO}
26271 The use of the standard child package syntax (for
26272 example, @code{ADA.TEXT_IO}) retrieves the post-Ada 83 versions of these
26274 GNAT provides HP-compatible predefined instantiations
26275 of the @code{TEXT_IO} packages, and also
26276 provides the standard predefined instantiations required
26277 by the @cite{Ada Reference Manual}.
26279 For further information on how GNAT interfaces to the file
26280 system or how I/O is implemented in programs written in
26281 mixed languages, see @ref{Implementation of the Standard I/O,,,
26282 gnat_rm, GNAT Reference Manual}.
26283 This chapter covers the following:
26285 @item Standard I/O packages
26287 @item @code{FORM} strings
26289 @item @code{ADA.DIRECT_IO}
26291 @item @code{ADA.SEQUENTIAL_IO}
26293 @item @code{ADA.TEXT_IO}
26295 @item Stream pointer positioning
26297 @item Reading and writing non-regular files
26299 @item @code{GET_IMMEDIATE}
26301 @item Treating @code{TEXT_IO} files as streams
26308 @node Implementation Limits
26309 @section Implementation Limits
26312 The following table lists implementation limits for HP Ada
26314 @multitable @columnfractions .60 .20 .20
26316 @item @emph{Compilation Parameter}
26321 @item In a subprogram or entry declaration, maximum number of
26322 formal parameters that are of an unconstrained record type
26327 @item Maximum identifier length (number of characters)
26332 @item Maximum number of characters in a source line
26337 @item Maximum collection size (number of bytes)
26342 @item Maximum number of discriminants for a record type
26347 @item Maximum number of formal parameters in an entry or
26348 subprogram declaration
26353 @item Maximum number of dimensions in an array type
26358 @item Maximum number of library units and subunits in a compilation.
26363 @item Maximum number of library units and subunits in an execution.
26368 @item Maximum number of objects declared with the pragma @code{COMMON_OBJECT}
26369 or @code{PSECT_OBJECT}
26374 @item Maximum number of enumeration literals in an enumeration type
26380 @item Maximum number of lines in a source file
26385 @item Maximum number of bits in any object
26390 @item Maximum size of the static portion of a stack frame (approximate)
26395 @node Tools and Utilities
26396 @section Tools and Utilities
26399 The following table lists some of the OpenVMS development tools
26400 available for HP Ada, and the corresponding tools for
26401 use with @value{EDITION} on Alpha and I64 platforms.
26402 Aside from the debugger, all the OpenVMS tools identified are part
26403 of the DECset package.
26406 @c Specify table in TeX since Texinfo does a poor job
26410 \settabs\+Language-Sensitive Editor\quad
26411 &Product with HP Ada\quad
26414 &\it Product with HP Ada
26415 & \it Product with GNAT Pro\cr
26417 \+Code Management System
26421 \+Language-Sensitive Editor
26423 & emacs or HP LSE (Alpha)\cr
26433 & OpenVMS Debug (I64)\cr
26435 \+Source Code Analyzer /
26452 \+Coverage Analyzer
26456 \+Module Management
26458 & Not applicable\cr
26468 @c This is the Texinfo version of the table. It renders poorly in pdf, hence
26469 @c the TeX version above for the printed version
26471 @c @multitable @columnfractions .3 .4 .4
26472 @multitable {Source Code Analyzer /}{Tool with HP Ada}{Tool with GNAT Pro}
26474 @tab @i{Tool with HP Ada}
26475 @tab @i{Tool with @value{EDITION}}
26476 @item Code Management@*System
26479 @item Language-Sensitive@*Editor
26481 @tab emacs or HP LSE (Alpha)
26490 @tab OpenVMS Debug (I64)
26491 @item Source Code Analyzer /@*Cross Referencer
26495 @tab HP Digital Test@*Manager (DTM)
26497 @item Performance and@*Coverage Analyzer
26500 @item Module Management@*System
26502 @tab Not applicable
26509 @c **************************************
26510 @node Platform-Specific Information for the Run-Time Libraries
26511 @appendix Platform-Specific Information for the Run-Time Libraries
26512 @cindex Tasking and threads libraries
26513 @cindex Threads libraries and tasking
26514 @cindex Run-time libraries (platform-specific information)
26517 The GNAT run-time implementation may vary with respect to both the
26518 underlying threads library and the exception handling scheme.
26519 For threads support, one or more of the following are supplied:
26521 @item @b{native threads library}, a binding to the thread package from
26522 the underlying operating system
26524 @item @b{pthreads library} (Sparc Solaris only), a binding to the Solaris
26525 POSIX thread package
26529 For exception handling, either or both of two models are supplied:
26531 @item @b{Zero-Cost Exceptions} (``ZCX''),@footnote{
26532 Most programs should experience a substantial speed improvement by
26533 being compiled with a ZCX run-time.
26534 This is especially true for
26535 tasking applications or applications with many exception handlers.}
26536 @cindex Zero-Cost Exceptions
26537 @cindex ZCX (Zero-Cost Exceptions)
26538 which uses binder-generated tables that
26539 are interrogated at run time to locate a handler
26541 @item @b{setjmp / longjmp} (``SJLJ''),
26542 @cindex setjmp/longjmp Exception Model
26543 @cindex SJLJ (setjmp/longjmp Exception Model)
26544 which uses dynamically-set data to establish
26545 the set of handlers
26549 This appendix summarizes which combinations of threads and exception support
26550 are supplied on various GNAT platforms.
26551 It then shows how to select a particular library either
26552 permanently or temporarily,
26553 explains the properties of (and tradeoffs among) the various threads
26554 libraries, and provides some additional
26555 information about several specific platforms.
26558 * Summary of Run-Time Configurations::
26559 * Specifying a Run-Time Library::
26560 * Choosing the Scheduling Policy::
26561 * Solaris-Specific Considerations::
26562 * Linux-Specific Considerations::
26563 * AIX-Specific Considerations::
26564 * Irix-Specific Considerations::
26565 * RTX-Specific Considerations::
26568 @node Summary of Run-Time Configurations
26569 @section Summary of Run-Time Configurations
26571 @multitable @columnfractions .30 .70
26572 @item @b{alpha-openvms}
26573 @item @code{@ @ }@i{rts-native (default)}
26574 @item @code{@ @ @ @ }Tasking @tab native VMS threads
26575 @item @code{@ @ @ @ }Exceptions @tab ZCX
26577 @item @b{alpha-tru64}
26578 @item @code{@ @ }@i{rts-native (default)}
26579 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
26580 @item @code{@ @ @ @ }Exceptions @tab ZCX
26582 @item @code{@ @ }@i{rts-sjlj}
26583 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
26584 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26586 @item @b{ia64-hp_linux}
26587 @item @code{@ @ }@i{rts-native (default)}
26588 @item @code{@ @ @ @ }Tasking @tab pthread library
26589 @item @code{@ @ @ @ }Exceptions @tab ZCX
26591 @item @b{ia64-hpux}
26592 @item @code{@ @ }@i{rts-native (default)}
26593 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26594 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26596 @item @b{ia64-openvms}
26597 @item @code{@ @ }@i{rts-native (default)}
26598 @item @code{@ @ @ @ }Tasking @tab native VMS threads
26599 @item @code{@ @ @ @ }Exceptions @tab ZCX
26601 @item @b{ia64-sgi_linux}
26602 @item @code{@ @ }@i{rts-native (default)}
26603 @item @code{@ @ @ @ }Tasking @tab pthread library
26604 @item @code{@ @ @ @ }Exceptions @tab ZCX
26606 @item @b{mips-irix}
26607 @item @code{@ @ }@i{rts-native (default)}
26608 @item @code{@ @ @ @ }Tasking @tab native IRIX threads
26609 @item @code{@ @ @ @ }Exceptions @tab ZCX
26612 @item @code{@ @ }@i{rts-native (default)}
26613 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26614 @item @code{@ @ @ @ }Exceptions @tab ZCX
26616 @item @code{@ @ }@i{rts-sjlj}
26617 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26618 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26621 @item @code{@ @ }@i{rts-native (default)}
26622 @item @code{@ @ @ @ }Tasking @tab native AIX threads
26623 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26625 @item @b{ppc-darwin}
26626 @item @code{@ @ }@i{rts-native (default)}
26627 @item @code{@ @ @ @ }Tasking @tab native MacOS threads
26628 @item @code{@ @ @ @ }Exceptions @tab ZCX
26630 @item @b{sparc-solaris} @tab
26631 @item @code{@ @ }@i{rts-native (default)}
26632 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26633 @item @code{@ @ @ @ }Exceptions @tab ZCX
26635 @item @code{@ @ }@i{rts-pthread}
26636 @item @code{@ @ @ @ }Tasking @tab pthread library
26637 @item @code{@ @ @ @ }Exceptions @tab ZCX
26639 @item @code{@ @ }@i{rts-sjlj}
26640 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26641 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26643 @item @b{sparc64-solaris} @tab
26644 @item @code{@ @ }@i{rts-native (default)}
26645 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26646 @item @code{@ @ @ @ }Exceptions @tab ZCX
26648 @item @b{x86-linux}
26649 @item @code{@ @ }@i{rts-native (default)}
26650 @item @code{@ @ @ @ }Tasking @tab pthread library
26651 @item @code{@ @ @ @ }Exceptions @tab ZCX
26653 @item @code{@ @ }@i{rts-sjlj}
26654 @item @code{@ @ @ @ }Tasking @tab pthread library
26655 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26658 @item @code{@ @ }@i{rts-native (default)}
26659 @item @code{@ @ @ @ }Tasking @tab native LynxOS threads
26660 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26662 @item @b{x86-solaris}
26663 @item @code{@ @ }@i{rts-native (default)}
26664 @item @code{@ @ @ @ }Tasking @tab native Solaris threads
26665 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26667 @item @b{x86-windows}
26668 @item @code{@ @ }@i{rts-native (default)}
26669 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
26670 @item @code{@ @ @ @ }Exceptions @tab ZCX
26672 @item @code{@ @ }@i{rts-sjlj (default)}
26673 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
26674 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26676 @item @b{x86-windows-rtx}
26677 @item @code{@ @ }@i{rts-rtx-rtss (default)}
26678 @item @code{@ @ @ @ }Tasking @tab RTX real-time subsystem RTSS threads (kernel mode)
26679 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26681 @item @code{@ @ }@i{rts-rtx-w32}
26682 @item @code{@ @ @ @ }Tasking @tab RTX Win32 threads (user mode)
26683 @item @code{@ @ @ @ }Exceptions @tab ZCX
26685 @item @b{x86_64-linux}
26686 @item @code{@ @ }@i{rts-native (default)}
26687 @item @code{@ @ @ @ }Tasking @tab pthread library
26688 @item @code{@ @ @ @ }Exceptions @tab ZCX
26690 @item @code{@ @ }@i{rts-sjlj}
26691 @item @code{@ @ @ @ }Tasking @tab pthread library
26692 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26696 @node Specifying a Run-Time Library
26697 @section Specifying a Run-Time Library
26700 The @file{adainclude} subdirectory containing the sources of the GNAT
26701 run-time library, and the @file{adalib} subdirectory containing the
26702 @file{ALI} files and the static and/or shared GNAT library, are located
26703 in the gcc target-dependent area:
26706 target=$prefix/lib/gcc/gcc-@i{dumpmachine}/gcc-@i{dumpversion}/
26710 As indicated above, on some platforms several run-time libraries are supplied.
26711 These libraries are installed in the target dependent area and
26712 contain a complete source and binary subdirectory. The detailed description
26713 below explains the differences between the different libraries in terms of
26714 their thread support.
26716 The default run-time library (when GNAT is installed) is @emph{rts-native}.
26717 This default run time is selected by the means of soft links.
26718 For example on x86-linux:
26724 +--- adainclude----------+
26726 +--- adalib-----------+ |
26728 +--- rts-native | |
26730 | +--- adainclude <---+
26732 | +--- adalib <----+
26743 If the @i{rts-sjlj} library is to be selected on a permanent basis,
26744 these soft links can be modified with the following commands:
26748 $ rm -f adainclude adalib
26749 $ ln -s rts-sjlj/adainclude adainclude
26750 $ ln -s rts-sjlj/adalib adalib
26754 Alternatively, you can specify @file{rts-sjlj/adainclude} in the file
26755 @file{$target/ada_source_path} and @file{rts-sjlj/adalib} in
26756 @file{$target/ada_object_path}.
26758 Selecting another run-time library temporarily can be
26759 achieved by using the @option{--RTS} switch, e.g., @option{--RTS=sjlj}
26760 @cindex @option{--RTS} option
26762 @node Choosing the Scheduling Policy
26763 @section Choosing the Scheduling Policy
26766 When using a POSIX threads implementation, you have a choice of several
26767 scheduling policies: @code{SCHED_FIFO},
26768 @cindex @code{SCHED_FIFO} scheduling policy
26770 @cindex @code{SCHED_RR} scheduling policy
26771 and @code{SCHED_OTHER}.
26772 @cindex @code{SCHED_OTHER} scheduling policy
26773 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
26774 or @code{SCHED_RR} requires special (e.g., root) privileges.
26776 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
26778 @cindex @code{SCHED_FIFO} scheduling policy
26779 you can use one of the following:
26783 @code{pragma Time_Slice (0.0)}
26784 @cindex pragma Time_Slice
26786 the corresponding binder option @option{-T0}
26787 @cindex @option{-T0} option
26789 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
26790 @cindex pragma Task_Dispatching_Policy
26794 To specify @code{SCHED_RR},
26795 @cindex @code{SCHED_RR} scheduling policy
26796 you should use @code{pragma Time_Slice} with a
26797 value greater than @code{0.0}, or else use the corresponding @option{-T}
26800 @node Solaris-Specific Considerations
26801 @section Solaris-Specific Considerations
26802 @cindex Solaris Sparc threads libraries
26805 This section addresses some topics related to the various threads libraries
26809 * Solaris Threads Issues::
26812 @node Solaris Threads Issues
26813 @subsection Solaris Threads Issues
26816 GNAT under Solaris/Sparc 32 bits comes with an alternate tasking run-time
26817 library based on POSIX threads --- @emph{rts-pthread}.
26818 @cindex rts-pthread threads library
26819 This run-time library has the advantage of being mostly shared across all
26820 POSIX-compliant thread implementations, and it also provides under
26821 @w{Solaris 8} the @code{PTHREAD_PRIO_INHERIT}
26822 @cindex @code{PTHREAD_PRIO_INHERIT} policy (under rts-pthread)
26823 and @code{PTHREAD_PRIO_PROTECT}
26824 @cindex @code{PTHREAD_PRIO_PROTECT} policy (under rts-pthread)
26825 semantics that can be selected using the predefined pragma
26826 @code{Locking_Policy}
26827 @cindex pragma Locking_Policy (under rts-pthread)
26829 @code{Inheritance_Locking} and @code{Ceiling_Locking} as the policy.
26830 @cindex @code{Inheritance_Locking} (under rts-pthread)
26831 @cindex @code{Ceiling_Locking} (under rts-pthread)
26833 As explained above, the native run-time library is based on the Solaris thread
26834 library (@code{libthread}) and is the default library.
26836 When the Solaris threads library is used (this is the default), programs
26837 compiled with GNAT can automatically take advantage of
26838 and can thus execute on multiple processors.
26839 The user can alternatively specify a processor on which the program should run
26840 to emulate a single-processor system. The multiprocessor / uniprocessor choice
26842 setting the environment variable @env{GNAT_PROCESSOR}
26843 @cindex @env{GNAT_PROCESSOR} environment variable (on Sparc Solaris)
26844 to one of the following:
26848 Use the default configuration (run the program on all
26849 available processors) - this is the same as having @code{GNAT_PROCESSOR}
26853 Let the run-time implementation choose one processor and run the program on
26856 @item 0 .. Last_Proc
26857 Run the program on the specified processor.
26858 @code{Last_Proc} is equal to @code{_SC_NPROCESSORS_CONF - 1}
26859 (where @code{_SC_NPROCESSORS_CONF} is a system variable).
26862 @node Linux-Specific Considerations
26863 @section Linux-Specific Considerations
26864 @cindex Linux threads libraries
26867 On GNU/Linux without NPTL support (usually system with GNU C Library
26868 older than 2.3), the signal model is not POSIX compliant, which means
26869 that to send a signal to the process, you need to send the signal to all
26870 threads, e.g.@: by using @code{killpg()}.
26872 @node AIX-Specific Considerations
26873 @section AIX-Specific Considerations
26874 @cindex AIX resolver library
26877 On AIX, the resolver library initializes some internal structure on
26878 the first call to @code{get*by*} functions, which are used to implement
26879 @code{GNAT.Sockets.Get_Host_By_Name} and
26880 @code{GNAT.Sockets.Get_Host_By_Address}.
26881 If such initialization occurs within an Ada task, and the stack size for
26882 the task is the default size, a stack overflow may occur.
26884 To avoid this overflow, the user should either ensure that the first call
26885 to @code{GNAT.Sockets.Get_Host_By_Name} or
26886 @code{GNAT.Sockets.Get_Host_By_Addrss}
26887 occurs in the environment task, or use @code{pragma Storage_Size} to
26888 specify a sufficiently large size for the stack of the task that contains
26891 @node Irix-Specific Considerations
26892 @section Irix-Specific Considerations
26893 @cindex Irix libraries
26896 The GCC support libraries coming with the Irix compiler have moved to
26897 their canonical place with respect to the general Irix ABI related
26898 conventions. Running applications built with the default shared GNAT
26899 run-time now requires the LD_LIBRARY_PATH environment variable to
26900 include this location. A possible way to achieve this is to issue the
26901 following command line on a bash prompt:
26905 $ LD_LIBRARY_PATH=$LD_LIBRARY_PATH:`dirname \`gcc --print-file-name=libgcc_s.so\``
26909 @node RTX-Specific Considerations
26910 @section RTX-Specific Considerations
26911 @cindex RTX libraries
26914 The Real-time Extension (RTX) to Windows is based on the Windows Win32
26915 API. Applications can be built to work in two different modes:
26919 Windows executables that run in Ring 3 to utilize memory protection
26920 (@emph{rts-rtx-w32}).
26923 Real-time subsystem (RTSS) executables that run in Ring 0, where
26924 performance can be optimized with RTSS applications taking precedent
26925 over all Windows applications (@emph{rts-rtx-rtss}).
26929 @c *******************************
26930 @node Example of Binder Output File
26931 @appendix Example of Binder Output File
26934 This Appendix displays the source code for @command{gnatbind}'s output
26935 file generated for a simple ``Hello World'' program.
26936 Comments have been added for clarification purposes.
26938 @smallexample @c adanocomment
26942 -- The package is called Ada_Main unless this name is actually used
26943 -- as a unit name in the partition, in which case some other unique
26947 package ada_main is
26949 Elab_Final_Code : Integer;
26950 pragma Import (C, Elab_Final_Code, "__gnat_inside_elab_final_code");
26952 -- The main program saves the parameters (argument count,
26953 -- argument values, environment pointer) in global variables
26954 -- for later access by other units including
26955 -- Ada.Command_Line.
26957 gnat_argc : Integer;
26958 gnat_argv : System.Address;
26959 gnat_envp : System.Address;
26961 -- The actual variables are stored in a library routine. This
26962 -- is useful for some shared library situations, where there
26963 -- are problems if variables are not in the library.
26965 pragma Import (C, gnat_argc);
26966 pragma Import (C, gnat_argv);
26967 pragma Import (C, gnat_envp);
26969 -- The exit status is similarly an external location
26971 gnat_exit_status : Integer;
26972 pragma Import (C, gnat_exit_status);
26974 GNAT_Version : constant String :=
26975 "GNAT Version: 6.0.0w (20061115)";
26976 pragma Export (C, GNAT_Version, "__gnat_version");
26978 -- This is the generated adafinal routine that performs
26979 -- finalization at the end of execution. In the case where
26980 -- Ada is the main program, this main program makes a call
26981 -- to adafinal at program termination.
26983 procedure adafinal;
26984 pragma Export (C, adafinal, "adafinal");
26986 -- This is the generated adainit routine that performs
26987 -- initialization at the start of execution. In the case
26988 -- where Ada is the main program, this main program makes
26989 -- a call to adainit at program startup.
26992 pragma Export (C, adainit, "adainit");
26994 -- This routine is called at the start of execution. It is
26995 -- a dummy routine that is used by the debugger to breakpoint
26996 -- at the start of execution.
26998 procedure Break_Start;
26999 pragma Import (C, Break_Start, "__gnat_break_start");
27001 -- This is the actual generated main program (it would be
27002 -- suppressed if the no main program switch were used). As
27003 -- required by standard system conventions, this program has
27004 -- the external name main.
27008 argv : System.Address;
27009 envp : System.Address)
27011 pragma Export (C, main, "main");
27013 -- The following set of constants give the version
27014 -- identification values for every unit in the bound
27015 -- partition. This identification is computed from all
27016 -- dependent semantic units, and corresponds to the
27017 -- string that would be returned by use of the
27018 -- Body_Version or Version attributes.
27020 type Version_32 is mod 2 ** 32;
27021 u00001 : constant Version_32 := 16#7880BEB3#;
27022 u00002 : constant Version_32 := 16#0D24CBD0#;
27023 u00003 : constant Version_32 := 16#3283DBEB#;
27024 u00004 : constant Version_32 := 16#2359F9ED#;
27025 u00005 : constant Version_32 := 16#664FB847#;
27026 u00006 : constant Version_32 := 16#68E803DF#;
27027 u00007 : constant Version_32 := 16#5572E604#;
27028 u00008 : constant Version_32 := 16#46B173D8#;
27029 u00009 : constant Version_32 := 16#156A40CF#;
27030 u00010 : constant Version_32 := 16#033DABE0#;
27031 u00011 : constant Version_32 := 16#6AB38FEA#;
27032 u00012 : constant Version_32 := 16#22B6217D#;
27033 u00013 : constant Version_32 := 16#68A22947#;
27034 u00014 : constant Version_32 := 16#18CC4A56#;
27035 u00015 : constant Version_32 := 16#08258E1B#;
27036 u00016 : constant Version_32 := 16#367D5222#;
27037 u00017 : constant Version_32 := 16#20C9ECA4#;
27038 u00018 : constant Version_32 := 16#50D32CB6#;
27039 u00019 : constant Version_32 := 16#39A8BB77#;
27040 u00020 : constant Version_32 := 16#5CF8FA2B#;
27041 u00021 : constant Version_32 := 16#2F1EB794#;
27042 u00022 : constant Version_32 := 16#31AB6444#;
27043 u00023 : constant Version_32 := 16#1574B6E9#;
27044 u00024 : constant Version_32 := 16#5109C189#;
27045 u00025 : constant Version_32 := 16#56D770CD#;
27046 u00026 : constant Version_32 := 16#02F9DE3D#;
27047 u00027 : constant Version_32 := 16#08AB6B2C#;
27048 u00028 : constant Version_32 := 16#3FA37670#;
27049 u00029 : constant Version_32 := 16#476457A0#;
27050 u00030 : constant Version_32 := 16#731E1B6E#;
27051 u00031 : constant Version_32 := 16#23C2E789#;
27052 u00032 : constant Version_32 := 16#0F1BD6A1#;
27053 u00033 : constant Version_32 := 16#7C25DE96#;
27054 u00034 : constant Version_32 := 16#39ADFFA2#;
27055 u00035 : constant Version_32 := 16#571DE3E7#;
27056 u00036 : constant Version_32 := 16#5EB646AB#;
27057 u00037 : constant Version_32 := 16#4249379B#;
27058 u00038 : constant Version_32 := 16#0357E00A#;
27059 u00039 : constant Version_32 := 16#3784FB72#;
27060 u00040 : constant Version_32 := 16#2E723019#;
27061 u00041 : constant Version_32 := 16#623358EA#;
27062 u00042 : constant Version_32 := 16#107F9465#;
27063 u00043 : constant Version_32 := 16#6843F68A#;
27064 u00044 : constant Version_32 := 16#63305874#;
27065 u00045 : constant Version_32 := 16#31E56CE1#;
27066 u00046 : constant Version_32 := 16#02917970#;
27067 u00047 : constant Version_32 := 16#6CCBA70E#;
27068 u00048 : constant Version_32 := 16#41CD4204#;
27069 u00049 : constant Version_32 := 16#572E3F58#;
27070 u00050 : constant Version_32 := 16#20729FF5#;
27071 u00051 : constant Version_32 := 16#1D4F93E8#;
27072 u00052 : constant Version_32 := 16#30B2EC3D#;
27073 u00053 : constant Version_32 := 16#34054F96#;
27074 u00054 : constant Version_32 := 16#5A199860#;
27075 u00055 : constant Version_32 := 16#0E7F912B#;
27076 u00056 : constant Version_32 := 16#5760634A#;
27077 u00057 : constant Version_32 := 16#5D851835#;
27079 -- The following Export pragmas export the version numbers
27080 -- with symbolic names ending in B (for body) or S
27081 -- (for spec) so that they can be located in a link. The
27082 -- information provided here is sufficient to track down
27083 -- the exact versions of units used in a given build.
27085 pragma Export (C, u00001, "helloB");
27086 pragma Export (C, u00002, "system__standard_libraryB");
27087 pragma Export (C, u00003, "system__standard_libraryS");
27088 pragma Export (C, u00004, "adaS");
27089 pragma Export (C, u00005, "ada__text_ioB");
27090 pragma Export (C, u00006, "ada__text_ioS");
27091 pragma Export (C, u00007, "ada__exceptionsB");
27092 pragma Export (C, u00008, "ada__exceptionsS");
27093 pragma Export (C, u00009, "gnatS");
27094 pragma Export (C, u00010, "gnat__heap_sort_aB");
27095 pragma Export (C, u00011, "gnat__heap_sort_aS");
27096 pragma Export (C, u00012, "systemS");
27097 pragma Export (C, u00013, "system__exception_tableB");
27098 pragma Export (C, u00014, "system__exception_tableS");
27099 pragma Export (C, u00015, "gnat__htableB");
27100 pragma Export (C, u00016, "gnat__htableS");
27101 pragma Export (C, u00017, "system__exceptionsS");
27102 pragma Export (C, u00018, "system__machine_state_operationsB");
27103 pragma Export (C, u00019, "system__machine_state_operationsS");
27104 pragma Export (C, u00020, "system__machine_codeS");
27105 pragma Export (C, u00021, "system__storage_elementsB");
27106 pragma Export (C, u00022, "system__storage_elementsS");
27107 pragma Export (C, u00023, "system__secondary_stackB");
27108 pragma Export (C, u00024, "system__secondary_stackS");
27109 pragma Export (C, u00025, "system__parametersB");
27110 pragma Export (C, u00026, "system__parametersS");
27111 pragma Export (C, u00027, "system__soft_linksB");
27112 pragma Export (C, u00028, "system__soft_linksS");
27113 pragma Export (C, u00029, "system__stack_checkingB");
27114 pragma Export (C, u00030, "system__stack_checkingS");
27115 pragma Export (C, u00031, "system__tracebackB");
27116 pragma Export (C, u00032, "system__tracebackS");
27117 pragma Export (C, u00033, "ada__streamsS");
27118 pragma Export (C, u00034, "ada__tagsB");
27119 pragma Export (C, u00035, "ada__tagsS");
27120 pragma Export (C, u00036, "system__string_opsB");
27121 pragma Export (C, u00037, "system__string_opsS");
27122 pragma Export (C, u00038, "interfacesS");
27123 pragma Export (C, u00039, "interfaces__c_streamsB");
27124 pragma Export (C, u00040, "interfaces__c_streamsS");
27125 pragma Export (C, u00041, "system__file_ioB");
27126 pragma Export (C, u00042, "system__file_ioS");
27127 pragma Export (C, u00043, "ada__finalizationB");
27128 pragma Export (C, u00044, "ada__finalizationS");
27129 pragma Export (C, u00045, "system__finalization_rootB");
27130 pragma Export (C, u00046, "system__finalization_rootS");
27131 pragma Export (C, u00047, "system__finalization_implementationB");
27132 pragma Export (C, u00048, "system__finalization_implementationS");
27133 pragma Export (C, u00049, "system__string_ops_concat_3B");
27134 pragma Export (C, u00050, "system__string_ops_concat_3S");
27135 pragma Export (C, u00051, "system__stream_attributesB");
27136 pragma Export (C, u00052, "system__stream_attributesS");
27137 pragma Export (C, u00053, "ada__io_exceptionsS");
27138 pragma Export (C, u00054, "system__unsigned_typesS");
27139 pragma Export (C, u00055, "system__file_control_blockS");
27140 pragma Export (C, u00056, "ada__finalization__list_controllerB");
27141 pragma Export (C, u00057, "ada__finalization__list_controllerS");
27143 -- BEGIN ELABORATION ORDER
27146 -- gnat.heap_sort_a (spec)
27147 -- gnat.heap_sort_a (body)
27148 -- gnat.htable (spec)
27149 -- gnat.htable (body)
27150 -- interfaces (spec)
27152 -- system.machine_code (spec)
27153 -- system.parameters (spec)
27154 -- system.parameters (body)
27155 -- interfaces.c_streams (spec)
27156 -- interfaces.c_streams (body)
27157 -- system.standard_library (spec)
27158 -- ada.exceptions (spec)
27159 -- system.exception_table (spec)
27160 -- system.exception_table (body)
27161 -- ada.io_exceptions (spec)
27162 -- system.exceptions (spec)
27163 -- system.storage_elements (spec)
27164 -- system.storage_elements (body)
27165 -- system.machine_state_operations (spec)
27166 -- system.machine_state_operations (body)
27167 -- system.secondary_stack (spec)
27168 -- system.stack_checking (spec)
27169 -- system.soft_links (spec)
27170 -- system.soft_links (body)
27171 -- system.stack_checking (body)
27172 -- system.secondary_stack (body)
27173 -- system.standard_library (body)
27174 -- system.string_ops (spec)
27175 -- system.string_ops (body)
27178 -- ada.streams (spec)
27179 -- system.finalization_root (spec)
27180 -- system.finalization_root (body)
27181 -- system.string_ops_concat_3 (spec)
27182 -- system.string_ops_concat_3 (body)
27183 -- system.traceback (spec)
27184 -- system.traceback (body)
27185 -- ada.exceptions (body)
27186 -- system.unsigned_types (spec)
27187 -- system.stream_attributes (spec)
27188 -- system.stream_attributes (body)
27189 -- system.finalization_implementation (spec)
27190 -- system.finalization_implementation (body)
27191 -- ada.finalization (spec)
27192 -- ada.finalization (body)
27193 -- ada.finalization.list_controller (spec)
27194 -- ada.finalization.list_controller (body)
27195 -- system.file_control_block (spec)
27196 -- system.file_io (spec)
27197 -- system.file_io (body)
27198 -- ada.text_io (spec)
27199 -- ada.text_io (body)
27201 -- END ELABORATION ORDER
27205 -- The following source file name pragmas allow the generated file
27206 -- names to be unique for different main programs. They are needed
27207 -- since the package name will always be Ada_Main.
27209 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
27210 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
27212 -- Generated package body for Ada_Main starts here
27214 package body ada_main is
27216 -- The actual finalization is performed by calling the
27217 -- library routine in System.Standard_Library.Adafinal
27219 procedure Do_Finalize;
27220 pragma Import (C, Do_Finalize, "system__standard_library__adafinal");
27227 procedure adainit is
27229 -- These booleans are set to True once the associated unit has
27230 -- been elaborated. It is also used to avoid elaborating the
27231 -- same unit twice.
27234 pragma Import (Ada, E040, "interfaces__c_streams_E");
27237 pragma Import (Ada, E008, "ada__exceptions_E");
27240 pragma Import (Ada, E014, "system__exception_table_E");
27243 pragma Import (Ada, E053, "ada__io_exceptions_E");
27246 pragma Import (Ada, E017, "system__exceptions_E");
27249 pragma Import (Ada, E024, "system__secondary_stack_E");
27252 pragma Import (Ada, E030, "system__stack_checking_E");
27255 pragma Import (Ada, E028, "system__soft_links_E");
27258 pragma Import (Ada, E035, "ada__tags_E");
27261 pragma Import (Ada, E033, "ada__streams_E");
27264 pragma Import (Ada, E046, "system__finalization_root_E");
27267 pragma Import (Ada, E048, "system__finalization_implementation_E");
27270 pragma Import (Ada, E044, "ada__finalization_E");
27273 pragma Import (Ada, E057, "ada__finalization__list_controller_E");
27276 pragma Import (Ada, E055, "system__file_control_block_E");
27279 pragma Import (Ada, E042, "system__file_io_E");
27282 pragma Import (Ada, E006, "ada__text_io_E");
27284 -- Set_Globals is a library routine that stores away the
27285 -- value of the indicated set of global values in global
27286 -- variables within the library.
27288 procedure Set_Globals
27289 (Main_Priority : Integer;
27290 Time_Slice_Value : Integer;
27291 WC_Encoding : Character;
27292 Locking_Policy : Character;
27293 Queuing_Policy : Character;
27294 Task_Dispatching_Policy : Character;
27295 Adafinal : System.Address;
27296 Unreserve_All_Interrupts : Integer;
27297 Exception_Tracebacks : Integer);
27298 @findex __gnat_set_globals
27299 pragma Import (C, Set_Globals, "__gnat_set_globals");
27301 -- SDP_Table_Build is a library routine used to build the
27302 -- exception tables. See unit Ada.Exceptions in files
27303 -- a-except.ads/adb for full details of how zero cost
27304 -- exception handling works. This procedure, the call to
27305 -- it, and the two following tables are all omitted if the
27306 -- build is in longjmp/setjmp exception mode.
27308 @findex SDP_Table_Build
27309 @findex Zero Cost Exceptions
27310 procedure SDP_Table_Build
27311 (SDP_Addresses : System.Address;
27312 SDP_Count : Natural;
27313 Elab_Addresses : System.Address;
27314 Elab_Addr_Count : Natural);
27315 pragma Import (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
27317 -- Table of Unit_Exception_Table addresses. Used for zero
27318 -- cost exception handling to build the top level table.
27320 ST : aliased constant array (1 .. 23) of System.Address := (
27322 Ada.Text_Io'UET_Address,
27323 Ada.Exceptions'UET_Address,
27324 Gnat.Heap_Sort_A'UET_Address,
27325 System.Exception_Table'UET_Address,
27326 System.Machine_State_Operations'UET_Address,
27327 System.Secondary_Stack'UET_Address,
27328 System.Parameters'UET_Address,
27329 System.Soft_Links'UET_Address,
27330 System.Stack_Checking'UET_Address,
27331 System.Traceback'UET_Address,
27332 Ada.Streams'UET_Address,
27333 Ada.Tags'UET_Address,
27334 System.String_Ops'UET_Address,
27335 Interfaces.C_Streams'UET_Address,
27336 System.File_Io'UET_Address,
27337 Ada.Finalization'UET_Address,
27338 System.Finalization_Root'UET_Address,
27339 System.Finalization_Implementation'UET_Address,
27340 System.String_Ops_Concat_3'UET_Address,
27341 System.Stream_Attributes'UET_Address,
27342 System.File_Control_Block'UET_Address,
27343 Ada.Finalization.List_Controller'UET_Address);
27345 -- Table of addresses of elaboration routines. Used for
27346 -- zero cost exception handling to make sure these
27347 -- addresses are included in the top level procedure
27350 EA : aliased constant array (1 .. 23) of System.Address := (
27351 adainit'Code_Address,
27352 Do_Finalize'Code_Address,
27353 Ada.Exceptions'Elab_Spec'Address,
27354 System.Exceptions'Elab_Spec'Address,
27355 Interfaces.C_Streams'Elab_Spec'Address,
27356 System.Exception_Table'Elab_Body'Address,
27357 Ada.Io_Exceptions'Elab_Spec'Address,
27358 System.Stack_Checking'Elab_Spec'Address,
27359 System.Soft_Links'Elab_Body'Address,
27360 System.Secondary_Stack'Elab_Body'Address,
27361 Ada.Tags'Elab_Spec'Address,
27362 Ada.Tags'Elab_Body'Address,
27363 Ada.Streams'Elab_Spec'Address,
27364 System.Finalization_Root'Elab_Spec'Address,
27365 Ada.Exceptions'Elab_Body'Address,
27366 System.Finalization_Implementation'Elab_Spec'Address,
27367 System.Finalization_Implementation'Elab_Body'Address,
27368 Ada.Finalization'Elab_Spec'Address,
27369 Ada.Finalization.List_Controller'Elab_Spec'Address,
27370 System.File_Control_Block'Elab_Spec'Address,
27371 System.File_Io'Elab_Body'Address,
27372 Ada.Text_Io'Elab_Spec'Address,
27373 Ada.Text_Io'Elab_Body'Address);
27375 -- Start of processing for adainit
27379 -- Call SDP_Table_Build to build the top level procedure
27380 -- table for zero cost exception handling (omitted in
27381 -- longjmp/setjmp mode).
27383 SDP_Table_Build (ST'Address, 23, EA'Address, 23);
27385 -- Call Set_Globals to record various information for
27386 -- this partition. The values are derived by the binder
27387 -- from information stored in the ali files by the compiler.
27389 @findex __gnat_set_globals
27391 (Main_Priority => -1,
27392 -- Priority of main program, -1 if no pragma Priority used
27394 Time_Slice_Value => -1,
27395 -- Time slice from Time_Slice pragma, -1 if none used
27397 WC_Encoding => 'b',
27398 -- Wide_Character encoding used, default is brackets
27400 Locking_Policy => ' ',
27401 -- Locking_Policy used, default of space means not
27402 -- specified, otherwise it is the first character of
27403 -- the policy name.
27405 Queuing_Policy => ' ',
27406 -- Queuing_Policy used, default of space means not
27407 -- specified, otherwise it is the first character of
27408 -- the policy name.
27410 Task_Dispatching_Policy => ' ',
27411 -- Task_Dispatching_Policy used, default of space means
27412 -- not specified, otherwise first character of the
27415 Adafinal => System.Null_Address,
27416 -- Address of Adafinal routine, not used anymore
27418 Unreserve_All_Interrupts => 0,
27419 -- Set true if pragma Unreserve_All_Interrupts was used
27421 Exception_Tracebacks => 0);
27422 -- Indicates if exception tracebacks are enabled
27424 Elab_Final_Code := 1;
27426 -- Now we have the elaboration calls for all units in the partition.
27427 -- The Elab_Spec and Elab_Body attributes generate references to the
27428 -- implicit elaboration procedures generated by the compiler for
27429 -- each unit that requires elaboration.
27432 Interfaces.C_Streams'Elab_Spec;
27436 Ada.Exceptions'Elab_Spec;
27439 System.Exception_Table'Elab_Body;
27443 Ada.Io_Exceptions'Elab_Spec;
27447 System.Exceptions'Elab_Spec;
27451 System.Stack_Checking'Elab_Spec;
27454 System.Soft_Links'Elab_Body;
27459 System.Secondary_Stack'Elab_Body;
27463 Ada.Tags'Elab_Spec;
27466 Ada.Tags'Elab_Body;
27470 Ada.Streams'Elab_Spec;
27474 System.Finalization_Root'Elab_Spec;
27478 Ada.Exceptions'Elab_Body;
27482 System.Finalization_Implementation'Elab_Spec;
27485 System.Finalization_Implementation'Elab_Body;
27489 Ada.Finalization'Elab_Spec;
27493 Ada.Finalization.List_Controller'Elab_Spec;
27497 System.File_Control_Block'Elab_Spec;
27501 System.File_Io'Elab_Body;
27505 Ada.Text_Io'Elab_Spec;
27508 Ada.Text_Io'Elab_Body;
27512 Elab_Final_Code := 0;
27520 procedure adafinal is
27529 -- main is actually a function, as in the ANSI C standard,
27530 -- defined to return the exit status. The three parameters
27531 -- are the argument count, argument values and environment
27534 @findex Main Program
27537 argv : System.Address;
27538 envp : System.Address)
27541 -- The initialize routine performs low level system
27542 -- initialization using a standard library routine which
27543 -- sets up signal handling and performs any other
27544 -- required setup. The routine can be found in file
27547 @findex __gnat_initialize
27548 procedure initialize;
27549 pragma Import (C, initialize, "__gnat_initialize");
27551 -- The finalize routine performs low level system
27552 -- finalization using a standard library routine. The
27553 -- routine is found in file a-final.c and in the standard
27554 -- distribution is a dummy routine that does nothing, so
27555 -- really this is a hook for special user finalization.
27557 @findex __gnat_finalize
27558 procedure finalize;
27559 pragma Import (C, finalize, "__gnat_finalize");
27561 -- We get to the main program of the partition by using
27562 -- pragma Import because if we try to with the unit and
27563 -- call it Ada style, then not only do we waste time
27564 -- recompiling it, but also, we don't really know the right
27565 -- switches (e.g.@: identifier character set) to be used
27568 procedure Ada_Main_Program;
27569 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
27571 -- Start of processing for main
27574 -- Save global variables
27580 -- Call low level system initialization
27584 -- Call our generated Ada initialization routine
27588 -- This is the point at which we want the debugger to get
27593 -- Now we call the main program of the partition
27597 -- Perform Ada finalization
27601 -- Perform low level system finalization
27605 -- Return the proper exit status
27606 return (gnat_exit_status);
27609 -- This section is entirely comments, so it has no effect on the
27610 -- compilation of the Ada_Main package. It provides the list of
27611 -- object files and linker options, as well as some standard
27612 -- libraries needed for the link. The gnatlink utility parses
27613 -- this b~hello.adb file to read these comment lines to generate
27614 -- the appropriate command line arguments for the call to the
27615 -- system linker. The BEGIN/END lines are used for sentinels for
27616 -- this parsing operation.
27618 -- The exact file names will of course depend on the environment,
27619 -- host/target and location of files on the host system.
27621 @findex Object file list
27622 -- BEGIN Object file/option list
27625 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
27626 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
27627 -- END Object file/option list
27633 The Ada code in the above example is exactly what is generated by the
27634 binder. We have added comments to more clearly indicate the function
27635 of each part of the generated @code{Ada_Main} package.
27637 The code is standard Ada in all respects, and can be processed by any
27638 tools that handle Ada. In particular, it is possible to use the debugger
27639 in Ada mode to debug the generated @code{Ada_Main} package. For example,
27640 suppose that for reasons that you do not understand, your program is crashing
27641 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
27642 you can place a breakpoint on the call:
27644 @smallexample @c ada
27645 Ada.Text_Io'Elab_Body;
27649 and trace the elaboration routine for this package to find out where
27650 the problem might be (more usually of course you would be debugging
27651 elaboration code in your own application).
27653 @node Elaboration Order Handling in GNAT
27654 @appendix Elaboration Order Handling in GNAT
27655 @cindex Order of elaboration
27656 @cindex Elaboration control
27659 * Elaboration Code::
27660 * Checking the Elaboration Order::
27661 * Controlling the Elaboration Order::
27662 * Controlling Elaboration in GNAT - Internal Calls::
27663 * Controlling Elaboration in GNAT - External Calls::
27664 * Default Behavior in GNAT - Ensuring Safety::
27665 * Treatment of Pragma Elaborate::
27666 * Elaboration Issues for Library Tasks::
27667 * Mixing Elaboration Models::
27668 * What to Do If the Default Elaboration Behavior Fails::
27669 * Elaboration for Access-to-Subprogram Values::
27670 * Summary of Procedures for Elaboration Control::
27671 * Other Elaboration Order Considerations::
27675 This chapter describes the handling of elaboration code in Ada and
27676 in GNAT, and discusses how the order of elaboration of program units can
27677 be controlled in GNAT, either automatically or with explicit programming
27680 @node Elaboration Code
27681 @section Elaboration Code
27684 Ada provides rather general mechanisms for executing code at elaboration
27685 time, that is to say before the main program starts executing. Such code arises
27689 @item Initializers for variables.
27690 Variables declared at the library level, in package specs or bodies, can
27691 require initialization that is performed at elaboration time, as in:
27692 @smallexample @c ada
27694 Sqrt_Half : Float := Sqrt (0.5);
27698 @item Package initialization code
27699 Code in a @code{BEGIN-END} section at the outer level of a package body is
27700 executed as part of the package body elaboration code.
27702 @item Library level task allocators
27703 Tasks that are declared using task allocators at the library level
27704 start executing immediately and hence can execute at elaboration time.
27708 Subprogram calls are possible in any of these contexts, which means that
27709 any arbitrary part of the program may be executed as part of the elaboration
27710 code. It is even possible to write a program which does all its work at
27711 elaboration time, with a null main program, although stylistically this
27712 would usually be considered an inappropriate way to structure
27715 An important concern arises in the context of elaboration code:
27716 we have to be sure that it is executed in an appropriate order. What we
27717 have is a series of elaboration code sections, potentially one section
27718 for each unit in the program. It is important that these execute
27719 in the correct order. Correctness here means that, taking the above
27720 example of the declaration of @code{Sqrt_Half},
27721 if some other piece of
27722 elaboration code references @code{Sqrt_Half},
27723 then it must run after the
27724 section of elaboration code that contains the declaration of
27727 There would never be any order of elaboration problem if we made a rule
27728 that whenever you @code{with} a unit, you must elaborate both the spec and body
27729 of that unit before elaborating the unit doing the @code{with}'ing:
27731 @smallexample @c ada
27735 package Unit_2 is @dots{}
27741 would require that both the body and spec of @code{Unit_1} be elaborated
27742 before the spec of @code{Unit_2}. However, a rule like that would be far too
27743 restrictive. In particular, it would make it impossible to have routines
27744 in separate packages that were mutually recursive.
27746 You might think that a clever enough compiler could look at the actual
27747 elaboration code and determine an appropriate correct order of elaboration,
27748 but in the general case, this is not possible. Consider the following
27751 In the body of @code{Unit_1}, we have a procedure @code{Func_1}
27753 the variable @code{Sqrt_1}, which is declared in the elaboration code
27754 of the body of @code{Unit_1}:
27756 @smallexample @c ada
27758 Sqrt_1 : Float := Sqrt (0.1);
27763 The elaboration code of the body of @code{Unit_1} also contains:
27765 @smallexample @c ada
27768 if expression_1 = 1 then
27769 Q := Unit_2.Func_2;
27776 @code{Unit_2} is exactly parallel,
27777 it has a procedure @code{Func_2} that references
27778 the variable @code{Sqrt_2}, which is declared in the elaboration code of
27779 the body @code{Unit_2}:
27781 @smallexample @c ada
27783 Sqrt_2 : Float := Sqrt (0.1);
27788 The elaboration code of the body of @code{Unit_2} also contains:
27790 @smallexample @c ada
27793 if expression_2 = 2 then
27794 Q := Unit_1.Func_1;
27801 Now the question is, which of the following orders of elaboration is
27826 If you carefully analyze the flow here, you will see that you cannot tell
27827 at compile time the answer to this question.
27828 If @code{expression_1} is not equal to 1,
27829 and @code{expression_2} is not equal to 2,
27830 then either order is acceptable, because neither of the function calls is
27831 executed. If both tests evaluate to true, then neither order is acceptable
27832 and in fact there is no correct order.
27834 If one of the two expressions is true, and the other is false, then one
27835 of the above orders is correct, and the other is incorrect. For example,
27836 if @code{expression_1} /= 1 and @code{expression_2} = 2,
27837 then the call to @code{Func_1}
27838 will occur, but not the call to @code{Func_2.}
27839 This means that it is essential
27840 to elaborate the body of @code{Unit_1} before
27841 the body of @code{Unit_2}, so the first
27842 order of elaboration is correct and the second is wrong.
27844 By making @code{expression_1} and @code{expression_2}
27845 depend on input data, or perhaps
27846 the time of day, we can make it impossible for the compiler or binder
27847 to figure out which of these expressions will be true, and hence it
27848 is impossible to guarantee a safe order of elaboration at run time.
27850 @node Checking the Elaboration Order
27851 @section Checking the Elaboration Order
27854 In some languages that involve the same kind of elaboration problems,
27855 e.g.@: Java and C++, the programmer is expected to worry about these
27856 ordering problems himself, and it is common to
27857 write a program in which an incorrect elaboration order gives
27858 surprising results, because it references variables before they
27860 Ada is designed to be a safe language, and a programmer-beware approach is
27861 clearly not sufficient. Consequently, the language provides three lines
27865 @item Standard rules
27866 Some standard rules restrict the possible choice of elaboration
27867 order. In particular, if you @code{with} a unit, then its spec is always
27868 elaborated before the unit doing the @code{with}. Similarly, a parent
27869 spec is always elaborated before the child spec, and finally
27870 a spec is always elaborated before its corresponding body.
27872 @item Dynamic elaboration checks
27873 @cindex Elaboration checks
27874 @cindex Checks, elaboration
27875 Dynamic checks are made at run time, so that if some entity is accessed
27876 before it is elaborated (typically by means of a subprogram call)
27877 then the exception (@code{Program_Error}) is raised.
27879 @item Elaboration control
27880 Facilities are provided for the programmer to specify the desired order
27884 Let's look at these facilities in more detail. First, the rules for
27885 dynamic checking. One possible rule would be simply to say that the
27886 exception is raised if you access a variable which has not yet been
27887 elaborated. The trouble with this approach is that it could require
27888 expensive checks on every variable reference. Instead Ada has two
27889 rules which are a little more restrictive, but easier to check, and
27893 @item Restrictions on calls
27894 A subprogram can only be called at elaboration time if its body
27895 has been elaborated. The rules for elaboration given above guarantee
27896 that the spec of the subprogram has been elaborated before the
27897 call, but not the body. If this rule is violated, then the
27898 exception @code{Program_Error} is raised.
27900 @item Restrictions on instantiations
27901 A generic unit can only be instantiated if the body of the generic
27902 unit has been elaborated. Again, the rules for elaboration given above
27903 guarantee that the spec of the generic unit has been elaborated
27904 before the instantiation, but not the body. If this rule is
27905 violated, then the exception @code{Program_Error} is raised.
27909 The idea is that if the body has been elaborated, then any variables
27910 it references must have been elaborated; by checking for the body being
27911 elaborated we guarantee that none of its references causes any
27912 trouble. As we noted above, this is a little too restrictive, because a
27913 subprogram that has no non-local references in its body may in fact be safe
27914 to call. However, it really would be unsafe to rely on this, because
27915 it would mean that the caller was aware of details of the implementation
27916 in the body. This goes against the basic tenets of Ada.
27918 A plausible implementation can be described as follows.
27919 A Boolean variable is associated with each subprogram
27920 and each generic unit. This variable is initialized to False, and is set to
27921 True at the point body is elaborated. Every call or instantiation checks the
27922 variable, and raises @code{Program_Error} if the variable is False.
27924 Note that one might think that it would be good enough to have one Boolean
27925 variable for each package, but that would not deal with cases of trying
27926 to call a body in the same package as the call
27927 that has not been elaborated yet.
27928 Of course a compiler may be able to do enough analysis to optimize away
27929 some of the Boolean variables as unnecessary, and @code{GNAT} indeed
27930 does such optimizations, but still the easiest conceptual model is to
27931 think of there being one variable per subprogram.
27933 @node Controlling the Elaboration Order
27934 @section Controlling the Elaboration Order
27937 In the previous section we discussed the rules in Ada which ensure
27938 that @code{Program_Error} is raised if an incorrect elaboration order is
27939 chosen. This prevents erroneous executions, but we need mechanisms to
27940 specify a correct execution and avoid the exception altogether.
27941 To achieve this, Ada provides a number of features for controlling
27942 the order of elaboration. We discuss these features in this section.
27944 First, there are several ways of indicating to the compiler that a given
27945 unit has no elaboration problems:
27948 @item packages that do not require a body
27949 A library package that does not require a body does not permit
27950 a body (this rule was introduced in Ada 95).
27951 Thus if we have a such a package, as in:
27953 @smallexample @c ada
27956 package Definitions is
27958 type m is new integer;
27960 type a is array (1 .. 10) of m;
27961 type b is array (1 .. 20) of m;
27969 A package that @code{with}'s @code{Definitions} may safely instantiate
27970 @code{Definitions.Subp} because the compiler can determine that there
27971 definitely is no package body to worry about in this case
27974 @cindex pragma Pure
27976 Places sufficient restrictions on a unit to guarantee that
27977 no call to any subprogram in the unit can result in an
27978 elaboration problem. This means that the compiler does not need
27979 to worry about the point of elaboration of such units, and in
27980 particular, does not need to check any calls to any subprograms
27983 @item pragma Preelaborate
27984 @findex Preelaborate
27985 @cindex pragma Preelaborate
27986 This pragma places slightly less stringent restrictions on a unit than
27988 but these restrictions are still sufficient to ensure that there
27989 are no elaboration problems with any calls to the unit.
27991 @item pragma Elaborate_Body
27992 @findex Elaborate_Body
27993 @cindex pragma Elaborate_Body
27994 This pragma requires that the body of a unit be elaborated immediately
27995 after its spec. Suppose a unit @code{A} has such a pragma,
27996 and unit @code{B} does
27997 a @code{with} of unit @code{A}. Recall that the standard rules require
27998 the spec of unit @code{A}
27999 to be elaborated before the @code{with}'ing unit; given the pragma in
28000 @code{A}, we also know that the body of @code{A}
28001 will be elaborated before @code{B}, so
28002 that calls to @code{A} are safe and do not need a check.
28007 unlike pragma @code{Pure} and pragma @code{Preelaborate},
28009 @code{Elaborate_Body} does not guarantee that the program is
28010 free of elaboration problems, because it may not be possible
28011 to satisfy the requested elaboration order.
28012 Let's go back to the example with @code{Unit_1} and @code{Unit_2}.
28014 marks @code{Unit_1} as @code{Elaborate_Body},
28015 and not @code{Unit_2,} then the order of
28016 elaboration will be:
28028 Now that means that the call to @code{Func_1} in @code{Unit_2}
28029 need not be checked,
28030 it must be safe. But the call to @code{Func_2} in
28031 @code{Unit_1} may still fail if
28032 @code{Expression_1} is equal to 1,
28033 and the programmer must still take
28034 responsibility for this not being the case.
28036 If all units carry a pragma @code{Elaborate_Body}, then all problems are
28037 eliminated, except for calls entirely within a body, which are
28038 in any case fully under programmer control. However, using the pragma
28039 everywhere is not always possible.
28040 In particular, for our @code{Unit_1}/@code{Unit_2} example, if
28041 we marked both of them as having pragma @code{Elaborate_Body}, then
28042 clearly there would be no possible elaboration order.
28044 The above pragmas allow a server to guarantee safe use by clients, and
28045 clearly this is the preferable approach. Consequently a good rule
28046 is to mark units as @code{Pure} or @code{Preelaborate} if possible,
28047 and if this is not possible,
28048 mark them as @code{Elaborate_Body} if possible.
28049 As we have seen, there are situations where neither of these
28050 three pragmas can be used.
28051 So we also provide methods for clients to control the
28052 order of elaboration of the servers on which they depend:
28055 @item pragma Elaborate (unit)
28057 @cindex pragma Elaborate
28058 This pragma is placed in the context clause, after a @code{with} clause,
28059 and it requires that the body of the named unit be elaborated before
28060 the unit in which the pragma occurs. The idea is to use this pragma
28061 if the current unit calls at elaboration time, directly or indirectly,
28062 some subprogram in the named unit.
28064 @item pragma Elaborate_All (unit)
28065 @findex Elaborate_All
28066 @cindex pragma Elaborate_All
28067 This is a stronger version of the Elaborate pragma. Consider the
28071 Unit A @code{with}'s unit B and calls B.Func in elab code
28072 Unit B @code{with}'s unit C, and B.Func calls C.Func
28076 Now if we put a pragma @code{Elaborate (B)}
28077 in unit @code{A}, this ensures that the
28078 body of @code{B} is elaborated before the call, but not the
28079 body of @code{C}, so
28080 the call to @code{C.Func} could still cause @code{Program_Error} to
28083 The effect of a pragma @code{Elaborate_All} is stronger, it requires
28084 not only that the body of the named unit be elaborated before the
28085 unit doing the @code{with}, but also the bodies of all units that the
28086 named unit uses, following @code{with} links transitively. For example,
28087 if we put a pragma @code{Elaborate_All (B)} in unit @code{A},
28089 not only that the body of @code{B} be elaborated before @code{A},
28091 body of @code{C}, because @code{B} @code{with}'s @code{C}.
28095 We are now in a position to give a usage rule in Ada for avoiding
28096 elaboration problems, at least if dynamic dispatching and access to
28097 subprogram values are not used. We will handle these cases separately
28100 The rule is simple. If a unit has elaboration code that can directly or
28101 indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate
28102 a generic package in a @code{with}'ed unit,
28103 then if the @code{with}'ed unit does not have
28104 pragma @code{Pure} or @code{Preelaborate}, then the client should have
28105 a pragma @code{Elaborate_All}
28106 for the @code{with}'ed unit. By following this rule a client is
28107 assured that calls can be made without risk of an exception.
28109 For generic subprogram instantiations, the rule can be relaxed to
28110 require only a pragma @code{Elaborate} since elaborating the body
28111 of a subprogram cannot cause any transitive elaboration (we are
28112 not calling the subprogram in this case, just elaborating its
28115 If this rule is not followed, then a program may be in one of four
28119 @item No order exists
28120 No order of elaboration exists which follows the rules, taking into
28121 account any @code{Elaborate}, @code{Elaborate_All},
28122 or @code{Elaborate_Body} pragmas. In
28123 this case, an Ada compiler must diagnose the situation at bind
28124 time, and refuse to build an executable program.
28126 @item One or more orders exist, all incorrect
28127 One or more acceptable elaboration orders exist, and all of them
28128 generate an elaboration order problem. In this case, the binder
28129 can build an executable program, but @code{Program_Error} will be raised
28130 when the program is run.
28132 @item Several orders exist, some right, some incorrect
28133 One or more acceptable elaboration orders exists, and some of them
28134 work, and some do not. The programmer has not controlled
28135 the order of elaboration, so the binder may or may not pick one of
28136 the correct orders, and the program may or may not raise an
28137 exception when it is run. This is the worst case, because it means
28138 that the program may fail when moved to another compiler, or even
28139 another version of the same compiler.
28141 @item One or more orders exists, all correct
28142 One ore more acceptable elaboration orders exist, and all of them
28143 work. In this case the program runs successfully. This state of
28144 affairs can be guaranteed by following the rule we gave above, but
28145 may be true even if the rule is not followed.
28149 Note that one additional advantage of following our rules on the use
28150 of @code{Elaborate} and @code{Elaborate_All}
28151 is that the program continues to stay in the ideal (all orders OK) state
28152 even if maintenance
28153 changes some bodies of some units. Conversely, if a program that does
28154 not follow this rule happens to be safe at some point, this state of affairs
28155 may deteriorate silently as a result of maintenance changes.
28157 You may have noticed that the above discussion did not mention
28158 the use of @code{Elaborate_Body}. This was a deliberate omission. If you
28159 @code{with} an @code{Elaborate_Body} unit, it still may be the case that
28160 code in the body makes calls to some other unit, so it is still necessary
28161 to use @code{Elaborate_All} on such units.
28163 @node Controlling Elaboration in GNAT - Internal Calls
28164 @section Controlling Elaboration in GNAT - Internal Calls
28167 In the case of internal calls, i.e., calls within a single package, the
28168 programmer has full control over the order of elaboration, and it is up
28169 to the programmer to elaborate declarations in an appropriate order. For
28172 @smallexample @c ada
28175 function One return Float;
28179 function One return Float is
28188 will obviously raise @code{Program_Error} at run time, because function
28189 One will be called before its body is elaborated. In this case GNAT will
28190 generate a warning that the call will raise @code{Program_Error}:
28196 2. function One return Float;
28198 4. Q : Float := One;
28200 >>> warning: cannot call "One" before body is elaborated
28201 >>> warning: Program_Error will be raised at run time
28204 6. function One return Float is
28217 Note that in this particular case, it is likely that the call is safe, because
28218 the function @code{One} does not access any global variables.
28219 Nevertheless in Ada, we do not want the validity of the check to depend on
28220 the contents of the body (think about the separate compilation case), so this
28221 is still wrong, as we discussed in the previous sections.
28223 The error is easily corrected by rearranging the declarations so that the
28224 body of @code{One} appears before the declaration containing the call
28225 (note that in Ada 95 and Ada 2005,
28226 declarations can appear in any order, so there is no restriction that
28227 would prevent this reordering, and if we write:
28229 @smallexample @c ada
28232 function One return Float;
28234 function One return Float is
28245 then all is well, no warning is generated, and no
28246 @code{Program_Error} exception
28248 Things are more complicated when a chain of subprograms is executed:
28250 @smallexample @c ada
28253 function A return Integer;
28254 function B return Integer;
28255 function C return Integer;
28257 function B return Integer is begin return A; end;
28258 function C return Integer is begin return B; end;
28262 function A return Integer is begin return 1; end;
28268 Now the call to @code{C}
28269 at elaboration time in the declaration of @code{X} is correct, because
28270 the body of @code{C} is already elaborated,
28271 and the call to @code{B} within the body of
28272 @code{C} is correct, but the call
28273 to @code{A} within the body of @code{B} is incorrect, because the body
28274 of @code{A} has not been elaborated, so @code{Program_Error}
28275 will be raised on the call to @code{A}.
28276 In this case GNAT will generate a
28277 warning that @code{Program_Error} may be
28278 raised at the point of the call. Let's look at the warning:
28284 2. function A return Integer;
28285 3. function B return Integer;
28286 4. function C return Integer;
28288 6. function B return Integer is begin return A; end;
28290 >>> warning: call to "A" before body is elaborated may
28291 raise Program_Error
28292 >>> warning: "B" called at line 7
28293 >>> warning: "C" called at line 9
28295 7. function C return Integer is begin return B; end;
28297 9. X : Integer := C;
28299 11. function A return Integer is begin return 1; end;
28309 Note that the message here says ``may raise'', instead of the direct case,
28310 where the message says ``will be raised''. That's because whether
28312 actually called depends in general on run-time flow of control.
28313 For example, if the body of @code{B} said
28315 @smallexample @c ada
28318 function B return Integer is
28320 if some-condition-depending-on-input-data then
28331 then we could not know until run time whether the incorrect call to A would
28332 actually occur, so @code{Program_Error} might
28333 or might not be raised. It is possible for a compiler to
28334 do a better job of analyzing bodies, to
28335 determine whether or not @code{Program_Error}
28336 might be raised, but it certainly
28337 couldn't do a perfect job (that would require solving the halting problem
28338 and is provably impossible), and because this is a warning anyway, it does
28339 not seem worth the effort to do the analysis. Cases in which it
28340 would be relevant are rare.
28342 In practice, warnings of either of the forms given
28343 above will usually correspond to
28344 real errors, and should be examined carefully and eliminated.
28345 In the rare case where a warning is bogus, it can be suppressed by any of
28346 the following methods:
28350 Compile with the @option{-gnatws} switch set
28353 Suppress @code{Elaboration_Check} for the called subprogram
28356 Use pragma @code{Warnings_Off} to turn warnings off for the call
28360 For the internal elaboration check case,
28361 GNAT by default generates the
28362 necessary run-time checks to ensure
28363 that @code{Program_Error} is raised if any
28364 call fails an elaboration check. Of course this can only happen if a
28365 warning has been issued as described above. The use of pragma
28366 @code{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress
28367 some of these checks, meaning that it may be possible (but is not
28368 guaranteed) for a program to be able to call a subprogram whose body
28369 is not yet elaborated, without raising a @code{Program_Error} exception.
28371 @node Controlling Elaboration in GNAT - External Calls
28372 @section Controlling Elaboration in GNAT - External Calls
28375 The previous section discussed the case in which the execution of a
28376 particular thread of elaboration code occurred entirely within a
28377 single unit. This is the easy case to handle, because a programmer
28378 has direct and total control over the order of elaboration, and
28379 furthermore, checks need only be generated in cases which are rare
28380 and which the compiler can easily detect.
28381 The situation is more complex when separate compilation is taken into account.
28382 Consider the following:
28384 @smallexample @c ada
28388 function Sqrt (Arg : Float) return Float;
28391 package body Math is
28392 function Sqrt (Arg : Float) return Float is
28401 X : Float := Math.Sqrt (0.5);
28414 where @code{Main} is the main program. When this program is executed, the
28415 elaboration code must first be executed, and one of the jobs of the
28416 binder is to determine the order in which the units of a program are
28417 to be elaborated. In this case we have four units: the spec and body
28419 the spec of @code{Stuff} and the body of @code{Main}).
28420 In what order should the four separate sections of elaboration code
28423 There are some restrictions in the order of elaboration that the binder
28424 can choose. In particular, if unit U has a @code{with}
28425 for a package @code{X}, then you
28426 are assured that the spec of @code{X}
28427 is elaborated before U , but you are
28428 not assured that the body of @code{X}
28429 is elaborated before U.
28430 This means that in the above case, the binder is allowed to choose the
28441 but that's not good, because now the call to @code{Math.Sqrt}
28442 that happens during
28443 the elaboration of the @code{Stuff}
28444 spec happens before the body of @code{Math.Sqrt} is
28445 elaborated, and hence causes @code{Program_Error} exception to be raised.
28446 At first glance, one might say that the binder is misbehaving, because
28447 obviously you want to elaborate the body of something you @code{with}
28449 that is not a general rule that can be followed in all cases. Consider
28451 @smallexample @c ada
28454 package X is @dots{}
28456 package Y is @dots{}
28459 package body Y is @dots{}
28462 package body X is @dots{}
28468 This is a common arrangement, and, apart from the order of elaboration
28469 problems that might arise in connection with elaboration code, this works fine.
28470 A rule that says that you must first elaborate the body of anything you
28471 @code{with} cannot work in this case:
28472 the body of @code{X} @code{with}'s @code{Y},
28473 which means you would have to
28474 elaborate the body of @code{Y} first, but that @code{with}'s @code{X},
28476 you have to elaborate the body of @code{X} first, but @dots{} and we have a
28477 loop that cannot be broken.
28479 It is true that the binder can in many cases guess an order of elaboration
28480 that is unlikely to cause a @code{Program_Error}
28481 exception to be raised, and it tries to do so (in the
28482 above example of @code{Math/Stuff/Spec}, the GNAT binder will
28484 elaborate the body of @code{Math} right after its spec, so all will be well).
28486 However, a program that blindly relies on the binder to be helpful can
28487 get into trouble, as we discussed in the previous sections, so
28489 provides a number of facilities for assisting the programmer in
28490 developing programs that are robust with respect to elaboration order.
28492 @node Default Behavior in GNAT - Ensuring Safety
28493 @section Default Behavior in GNAT - Ensuring Safety
28496 The default behavior in GNAT ensures elaboration safety. In its
28497 default mode GNAT implements the
28498 rule we previously described as the right approach. Let's restate it:
28502 @emph{If a unit has elaboration code that can directly or indirectly make a
28503 call to a subprogram in a @code{with}'ed unit, or instantiate a generic
28504 package in a @code{with}'ed unit, then if the @code{with}'ed unit
28505 does not have pragma @code{Pure} or
28506 @code{Preelaborate}, then the client should have an
28507 @code{Elaborate_All} pragma for the @code{with}'ed unit.}
28509 @emph{In the case of instantiating a generic subprogram, it is always
28510 sufficient to have only an @code{Elaborate} pragma for the
28511 @code{with}'ed unit.}
28515 By following this rule a client is assured that calls and instantiations
28516 can be made without risk of an exception.
28518 In this mode GNAT traces all calls that are potentially made from
28519 elaboration code, and puts in any missing implicit @code{Elaborate}
28520 and @code{Elaborate_All} pragmas.
28521 The advantage of this approach is that no elaboration problems
28522 are possible if the binder can find an elaboration order that is
28523 consistent with these implicit @code{Elaborate} and
28524 @code{Elaborate_All} pragmas. The
28525 disadvantage of this approach is that no such order may exist.
28527 If the binder does not generate any diagnostics, then it means that it has
28528 found an elaboration order that is guaranteed to be safe. However, the binder
28529 may still be relying on implicitly generated @code{Elaborate} and
28530 @code{Elaborate_All} pragmas so portability to other compilers than GNAT is not
28533 If it is important to guarantee portability, then the compilations should
28536 (warn on elaboration problems) switch. This will cause warning messages
28537 to be generated indicating the missing @code{Elaborate} and
28538 @code{Elaborate_All} pragmas.
28539 Consider the following source program:
28541 @smallexample @c ada
28546 m : integer := k.r;
28553 where it is clear that there
28554 should be a pragma @code{Elaborate_All}
28555 for unit @code{k}. An implicit pragma will be generated, and it is
28556 likely that the binder will be able to honor it. However, if you want
28557 to port this program to some other Ada compiler than GNAT.
28558 it is safer to include the pragma explicitly in the source. If this
28559 unit is compiled with the
28561 switch, then the compiler outputs a warning:
28568 3. m : integer := k.r;
28570 >>> warning: call to "r" may raise Program_Error
28571 >>> warning: missing pragma Elaborate_All for "k"
28579 and these warnings can be used as a guide for supplying manually
28580 the missing pragmas. It is usually a bad idea to use this warning
28581 option during development. That's because it will warn you when
28582 you need to put in a pragma, but cannot warn you when it is time
28583 to take it out. So the use of pragma @code{Elaborate_All} may lead to
28584 unnecessary dependencies and even false circularities.
28586 This default mode is more restrictive than the Ada Reference
28587 Manual, and it is possible to construct programs which will compile
28588 using the dynamic model described there, but will run into a
28589 circularity using the safer static model we have described.
28591 Of course any Ada compiler must be able to operate in a mode
28592 consistent with the requirements of the Ada Reference Manual,
28593 and in particular must have the capability of implementing the
28594 standard dynamic model of elaboration with run-time checks.
28596 In GNAT, this standard mode can be achieved either by the use of
28597 the @option{-gnatE} switch on the compiler (@command{gcc} or
28598 @command{gnatmake}) command, or by the use of the configuration pragma:
28600 @smallexample @c ada
28601 pragma Elaboration_Checks (DYNAMIC);
28605 Either approach will cause the unit affected to be compiled using the
28606 standard dynamic run-time elaboration checks described in the Ada
28607 Reference Manual. The static model is generally preferable, since it
28608 is clearly safer to rely on compile and link time checks rather than
28609 run-time checks. However, in the case of legacy code, it may be
28610 difficult to meet the requirements of the static model. This
28611 issue is further discussed in
28612 @ref{What to Do If the Default Elaboration Behavior Fails}.
28614 Note that the static model provides a strict subset of the allowed
28615 behavior and programs of the Ada Reference Manual, so if you do
28616 adhere to the static model and no circularities exist,
28617 then you are assured that your program will
28618 work using the dynamic model, providing that you remove any
28619 pragma Elaborate statements from the source.
28621 @node Treatment of Pragma Elaborate
28622 @section Treatment of Pragma Elaborate
28623 @cindex Pragma Elaborate
28626 The use of @code{pragma Elaborate}
28627 should generally be avoided in Ada 95 and Ada 2005 programs,
28628 since there is no guarantee that transitive calls
28629 will be properly handled. Indeed at one point, this pragma was placed
28630 in Annex J (Obsolescent Features), on the grounds that it is never useful.
28632 Now that's a bit restrictive. In practice, the case in which
28633 @code{pragma Elaborate} is useful is when the caller knows that there
28634 are no transitive calls, or that the called unit contains all necessary
28635 transitive @code{pragma Elaborate} statements, and legacy code often
28636 contains such uses.
28638 Strictly speaking the static mode in GNAT should ignore such pragmas,
28639 since there is no assurance at compile time that the necessary safety
28640 conditions are met. In practice, this would cause GNAT to be incompatible
28641 with correctly written Ada 83 code that had all necessary
28642 @code{pragma Elaborate} statements in place. Consequently, we made the
28643 decision that GNAT in its default mode will believe that if it encounters
28644 a @code{pragma Elaborate} then the programmer knows what they are doing,
28645 and it will trust that no elaboration errors can occur.
28647 The result of this decision is two-fold. First to be safe using the
28648 static mode, you should remove all @code{pragma Elaborate} statements.
28649 Second, when fixing circularities in existing code, you can selectively
28650 use @code{pragma Elaborate} statements to convince the static mode of
28651 GNAT that it need not generate an implicit @code{pragma Elaborate_All}
28654 When using the static mode with @option{-gnatwl}, any use of
28655 @code{pragma Elaborate} will generate a warning about possible
28658 @node Elaboration Issues for Library Tasks
28659 @section Elaboration Issues for Library Tasks
28660 @cindex Library tasks, elaboration issues
28661 @cindex Elaboration of library tasks
28664 In this section we examine special elaboration issues that arise for
28665 programs that declare library level tasks.
28667 Generally the model of execution of an Ada program is that all units are
28668 elaborated, and then execution of the program starts. However, the
28669 declaration of library tasks definitely does not fit this model. The
28670 reason for this is that library tasks start as soon as they are declared
28671 (more precisely, as soon as the statement part of the enclosing package
28672 body is reached), that is to say before elaboration
28673 of the program is complete. This means that if such a task calls a
28674 subprogram, or an entry in another task, the callee may or may not be
28675 elaborated yet, and in the standard
28676 Reference Manual model of dynamic elaboration checks, you can even
28677 get timing dependent Program_Error exceptions, since there can be
28678 a race between the elaboration code and the task code.
28680 The static model of elaboration in GNAT seeks to avoid all such
28681 dynamic behavior, by being conservative, and the conservative
28682 approach in this particular case is to assume that all the code
28683 in a task body is potentially executed at elaboration time if
28684 a task is declared at the library level.
28686 This can definitely result in unexpected circularities. Consider
28687 the following example
28689 @smallexample @c ada
28695 type My_Int is new Integer;
28697 function Ident (M : My_Int) return My_Int;
28701 package body Decls is
28702 task body Lib_Task is
28708 function Ident (M : My_Int) return My_Int is
28716 procedure Put_Val (Arg : Decls.My_Int);
28720 package body Utils is
28721 procedure Put_Val (Arg : Decls.My_Int) is
28723 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
28730 Decls.Lib_Task.Start;
28735 If the above example is compiled in the default static elaboration
28736 mode, then a circularity occurs. The circularity comes from the call
28737 @code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since
28738 this call occurs in elaboration code, we need an implicit pragma
28739 @code{Elaborate_All} for @code{Utils}. This means that not only must
28740 the spec and body of @code{Utils} be elaborated before the body
28741 of @code{Decls}, but also the spec and body of any unit that is
28742 @code{with'ed} by the body of @code{Utils} must also be elaborated before
28743 the body of @code{Decls}. This is the transitive implication of
28744 pragma @code{Elaborate_All} and it makes sense, because in general
28745 the body of @code{Put_Val} might have a call to something in a
28746 @code{with'ed} unit.
28748 In this case, the body of Utils (actually its spec) @code{with's}
28749 @code{Decls}. Unfortunately this means that the body of @code{Decls}
28750 must be elaborated before itself, in case there is a call from the
28751 body of @code{Utils}.
28753 Here is the exact chain of events we are worrying about:
28757 In the body of @code{Decls} a call is made from within the body of a library
28758 task to a subprogram in the package @code{Utils}. Since this call may
28759 occur at elaboration time (given that the task is activated at elaboration
28760 time), we have to assume the worst, i.e., that the
28761 call does happen at elaboration time.
28764 This means that the body and spec of @code{Util} must be elaborated before
28765 the body of @code{Decls} so that this call does not cause an access before
28769 Within the body of @code{Util}, specifically within the body of
28770 @code{Util.Put_Val} there may be calls to any unit @code{with}'ed
28774 One such @code{with}'ed package is package @code{Decls}, so there
28775 might be a call to a subprogram in @code{Decls} in @code{Put_Val}.
28776 In fact there is such a call in this example, but we would have to
28777 assume that there was such a call even if it were not there, since
28778 we are not supposed to write the body of @code{Decls} knowing what
28779 is in the body of @code{Utils}; certainly in the case of the
28780 static elaboration model, the compiler does not know what is in
28781 other bodies and must assume the worst.
28784 This means that the spec and body of @code{Decls} must also be
28785 elaborated before we elaborate the unit containing the call, but
28786 that unit is @code{Decls}! This means that the body of @code{Decls}
28787 must be elaborated before itself, and that's a circularity.
28791 Indeed, if you add an explicit pragma @code{Elaborate_All} for @code{Utils} in
28792 the body of @code{Decls} you will get a true Ada Reference Manual
28793 circularity that makes the program illegal.
28795 In practice, we have found that problems with the static model of
28796 elaboration in existing code often arise from library tasks, so
28797 we must address this particular situation.
28799 Note that if we compile and run the program above, using the dynamic model of
28800 elaboration (that is to say use the @option{-gnatE} switch),
28801 then it compiles, binds,
28802 links, and runs, printing the expected result of 2. Therefore in some sense
28803 the circularity here is only apparent, and we need to capture
28804 the properties of this program that distinguish it from other library-level
28805 tasks that have real elaboration problems.
28807 We have four possible answers to this question:
28812 Use the dynamic model of elaboration.
28814 If we use the @option{-gnatE} switch, then as noted above, the program works.
28815 Why is this? If we examine the task body, it is apparent that the task cannot
28817 @code{accept} statement until after elaboration has been completed, because
28818 the corresponding entry call comes from the main program, not earlier.
28819 This is why the dynamic model works here. But that's really giving
28820 up on a precise analysis, and we prefer to take this approach only if we cannot
28822 problem in any other manner. So let us examine two ways to reorganize
28823 the program to avoid the potential elaboration problem.
28826 Split library tasks into separate packages.
28828 Write separate packages, so that library tasks are isolated from
28829 other declarations as much as possible. Let us look at a variation on
28832 @smallexample @c ada
28840 package body Decls1 is
28841 task body Lib_Task is
28849 type My_Int is new Integer;
28850 function Ident (M : My_Int) return My_Int;
28854 package body Decls2 is
28855 function Ident (M : My_Int) return My_Int is
28863 procedure Put_Val (Arg : Decls2.My_Int);
28867 package body Utils is
28868 procedure Put_Val (Arg : Decls2.My_Int) is
28870 Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
28877 Decls1.Lib_Task.Start;
28882 All we have done is to split @code{Decls} into two packages, one
28883 containing the library task, and one containing everything else. Now
28884 there is no cycle, and the program compiles, binds, links and executes
28885 using the default static model of elaboration.
28888 Declare separate task types.
28890 A significant part of the problem arises because of the use of the
28891 single task declaration form. This means that the elaboration of
28892 the task type, and the elaboration of the task itself (i.e.@: the
28893 creation of the task) happen at the same time. A good rule
28894 of style in Ada is to always create explicit task types. By
28895 following the additional step of placing task objects in separate
28896 packages from the task type declaration, many elaboration problems
28897 are avoided. Here is another modified example of the example program:
28899 @smallexample @c ada
28901 task type Lib_Task_Type is
28905 type My_Int is new Integer;
28907 function Ident (M : My_Int) return My_Int;
28911 package body Decls is
28912 task body Lib_Task_Type is
28918 function Ident (M : My_Int) return My_Int is
28926 procedure Put_Val (Arg : Decls.My_Int);
28930 package body Utils is
28931 procedure Put_Val (Arg : Decls.My_Int) is
28933 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
28939 Lib_Task : Decls.Lib_Task_Type;
28945 Declst.Lib_Task.Start;
28950 What we have done here is to replace the @code{task} declaration in
28951 package @code{Decls} with a @code{task type} declaration. Then we
28952 introduce a separate package @code{Declst} to contain the actual
28953 task object. This separates the elaboration issues for
28954 the @code{task type}
28955 declaration, which causes no trouble, from the elaboration issues
28956 of the task object, which is also unproblematic, since it is now independent
28957 of the elaboration of @code{Utils}.
28958 This separation of concerns also corresponds to
28959 a generally sound engineering principle of separating declarations
28960 from instances. This version of the program also compiles, binds, links,
28961 and executes, generating the expected output.
28964 Use No_Entry_Calls_In_Elaboration_Code restriction.
28965 @cindex No_Entry_Calls_In_Elaboration_Code
28967 The previous two approaches described how a program can be restructured
28968 to avoid the special problems caused by library task bodies. in practice,
28969 however, such restructuring may be difficult to apply to existing legacy code,
28970 so we must consider solutions that do not require massive rewriting.
28972 Let us consider more carefully why our original sample program works
28973 under the dynamic model of elaboration. The reason is that the code
28974 in the task body blocks immediately on the @code{accept}
28975 statement. Now of course there is nothing to prohibit elaboration
28976 code from making entry calls (for example from another library level task),
28977 so we cannot tell in isolation that
28978 the task will not execute the accept statement during elaboration.
28980 However, in practice it is very unusual to see elaboration code
28981 make any entry calls, and the pattern of tasks starting
28982 at elaboration time and then immediately blocking on @code{accept} or
28983 @code{select} statements is very common. What this means is that
28984 the compiler is being too pessimistic when it analyzes the
28985 whole package body as though it might be executed at elaboration
28988 If we know that the elaboration code contains no entry calls, (a very safe
28989 assumption most of the time, that could almost be made the default
28990 behavior), then we can compile all units of the program under control
28991 of the following configuration pragma:
28994 pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
28998 This pragma can be placed in the @file{gnat.adc} file in the usual
28999 manner. If we take our original unmodified program and compile it
29000 in the presence of a @file{gnat.adc} containing the above pragma,
29001 then once again, we can compile, bind, link, and execute, obtaining
29002 the expected result. In the presence of this pragma, the compiler does
29003 not trace calls in a task body, that appear after the first @code{accept}
29004 or @code{select} statement, and therefore does not report a potential
29005 circularity in the original program.
29007 The compiler will check to the extent it can that the above
29008 restriction is not violated, but it is not always possible to do a
29009 complete check at compile time, so it is important to use this
29010 pragma only if the stated restriction is in fact met, that is to say
29011 no task receives an entry call before elaboration of all units is completed.
29015 @node Mixing Elaboration Models
29016 @section Mixing Elaboration Models
29018 So far, we have assumed that the entire program is either compiled
29019 using the dynamic model or static model, ensuring consistency. It
29020 is possible to mix the two models, but rules have to be followed
29021 if this mixing is done to ensure that elaboration checks are not
29024 The basic rule is that @emph{a unit compiled with the static model cannot
29025 be @code{with'ed} by a unit compiled with the dynamic model}. The
29026 reason for this is that in the static model, a unit assumes that
29027 its clients guarantee to use (the equivalent of) pragma
29028 @code{Elaborate_All} so that no elaboration checks are required
29029 in inner subprograms, and this assumption is violated if the
29030 client is compiled with dynamic checks.
29032 The precise rule is as follows. A unit that is compiled with dynamic
29033 checks can only @code{with} a unit that meets at least one of the
29034 following criteria:
29039 The @code{with'ed} unit is itself compiled with dynamic elaboration
29040 checks (that is with the @option{-gnatE} switch.
29043 The @code{with'ed} unit is an internal GNAT implementation unit from
29044 the System, Interfaces, Ada, or GNAT hierarchies.
29047 The @code{with'ed} unit has pragma Preelaborate or pragma Pure.
29050 The @code{with'ing} unit (that is the client) has an explicit pragma
29051 @code{Elaborate_All} for the @code{with'ed} unit.
29056 If this rule is violated, that is if a unit with dynamic elaboration
29057 checks @code{with's} a unit that does not meet one of the above four
29058 criteria, then the binder (@code{gnatbind}) will issue a warning
29059 similar to that in the following example:
29062 warning: "x.ads" has dynamic elaboration checks and with's
29063 warning: "y.ads" which has static elaboration checks
29067 These warnings indicate that the rule has been violated, and that as a result
29068 elaboration checks may be missed in the resulting executable file.
29069 This warning may be suppressed using the @option{-ws} binder switch
29070 in the usual manner.
29072 One useful application of this mixing rule is in the case of a subsystem
29073 which does not itself @code{with} units from the remainder of the
29074 application. In this case, the entire subsystem can be compiled with
29075 dynamic checks to resolve a circularity in the subsystem, while
29076 allowing the main application that uses this subsystem to be compiled
29077 using the more reliable default static model.
29079 @node What to Do If the Default Elaboration Behavior Fails
29080 @section What to Do If the Default Elaboration Behavior Fails
29083 If the binder cannot find an acceptable order, it outputs detailed
29084 diagnostics. For example:
29090 error: elaboration circularity detected
29091 info: "proc (body)" must be elaborated before "pack (body)"
29092 info: reason: Elaborate_All probably needed in unit "pack (body)"
29093 info: recompile "pack (body)" with -gnatwl
29094 info: for full details
29095 info: "proc (body)"
29096 info: is needed by its spec:
29097 info: "proc (spec)"
29098 info: which is withed by:
29099 info: "pack (body)"
29100 info: "pack (body)" must be elaborated before "proc (body)"
29101 info: reason: pragma Elaborate in unit "proc (body)"
29107 In this case we have a cycle that the binder cannot break. On the one
29108 hand, there is an explicit pragma Elaborate in @code{proc} for
29109 @code{pack}. This means that the body of @code{pack} must be elaborated
29110 before the body of @code{proc}. On the other hand, there is elaboration
29111 code in @code{pack} that calls a subprogram in @code{proc}. This means
29112 that for maximum safety, there should really be a pragma
29113 Elaborate_All in @code{pack} for @code{proc} which would require that
29114 the body of @code{proc} be elaborated before the body of
29115 @code{pack}. Clearly both requirements cannot be satisfied.
29116 Faced with a circularity of this kind, you have three different options.
29119 @item Fix the program
29120 The most desirable option from the point of view of long-term maintenance
29121 is to rearrange the program so that the elaboration problems are avoided.
29122 One useful technique is to place the elaboration code into separate
29123 child packages. Another is to move some of the initialization code to
29124 explicitly called subprograms, where the program controls the order
29125 of initialization explicitly. Although this is the most desirable option,
29126 it may be impractical and involve too much modification, especially in
29127 the case of complex legacy code.
29129 @item Perform dynamic checks
29130 If the compilations are done using the
29132 (dynamic elaboration check) switch, then GNAT behaves in a quite different
29133 manner. Dynamic checks are generated for all calls that could possibly result
29134 in raising an exception. With this switch, the compiler does not generate
29135 implicit @code{Elaborate} or @code{Elaborate_All} pragmas. The behavior then is
29136 exactly as specified in the @cite{Ada Reference Manual}.
29137 The binder will generate
29138 an executable program that may or may not raise @code{Program_Error}, and then
29139 it is the programmer's job to ensure that it does not raise an exception. Note
29140 that it is important to compile all units with the switch, it cannot be used
29143 @item Suppress checks
29144 The drawback of dynamic checks is that they generate a
29145 significant overhead at run time, both in space and time. If you
29146 are absolutely sure that your program cannot raise any elaboration
29147 exceptions, and you still want to use the dynamic elaboration model,
29148 then you can use the configuration pragma
29149 @code{Suppress (Elaboration_Check)} to suppress all such checks. For
29150 example this pragma could be placed in the @file{gnat.adc} file.
29152 @item Suppress checks selectively
29153 When you know that certain calls or instantiations in elaboration code cannot
29154 possibly lead to an elaboration error, and the binder nevertheless complains
29155 about implicit @code{Elaborate} and @code{Elaborate_All} pragmas that lead to
29156 elaboration circularities, it is possible to remove those warnings locally and
29157 obtain a program that will bind. Clearly this can be unsafe, and it is the
29158 responsibility of the programmer to make sure that the resulting program has no
29159 elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can be
29160 used with different granularity to suppress warnings and break elaboration
29165 Place the pragma that names the called subprogram in the declarative part
29166 that contains the call.
29169 Place the pragma in the declarative part, without naming an entity. This
29170 disables warnings on all calls in the corresponding declarative region.
29173 Place the pragma in the package spec that declares the called subprogram,
29174 and name the subprogram. This disables warnings on all elaboration calls to
29178 Place the pragma in the package spec that declares the called subprogram,
29179 without naming any entity. This disables warnings on all elaboration calls to
29180 all subprograms declared in this spec.
29182 @item Use Pragma Elaborate
29183 As previously described in section @xref{Treatment of Pragma Elaborate},
29184 GNAT in static mode assumes that a @code{pragma} Elaborate indicates correctly
29185 that no elaboration checks are required on calls to the designated unit.
29186 There may be cases in which the caller knows that no transitive calls
29187 can occur, so that a @code{pragma Elaborate} will be sufficient in a
29188 case where @code{pragma Elaborate_All} would cause a circularity.
29192 These five cases are listed in order of decreasing safety, and therefore
29193 require increasing programmer care in their application. Consider the
29196 @smallexample @c adanocomment
29198 function F1 return Integer;
29203 function F2 return Integer;
29204 function Pure (x : integer) return integer;
29205 -- pragma Suppress (Elaboration_Check, On => Pure); -- (3)
29206 -- pragma Suppress (Elaboration_Check); -- (4)
29210 package body Pack1 is
29211 function F1 return Integer is
29215 Val : integer := Pack2.Pure (11); -- Elab. call (1)
29218 -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1)
29219 -- pragma Suppress(Elaboration_Check); -- (2)
29221 X1 := Pack2.F2 + 1; -- Elab. call (2)
29226 package body Pack2 is
29227 function F2 return Integer is
29231 function Pure (x : integer) return integer is
29233 return x ** 3 - 3 * x;
29237 with Pack1, Ada.Text_IO;
29240 Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
29243 In the absence of any pragmas, an attempt to bind this program produces
29244 the following diagnostics:
29250 error: elaboration circularity detected
29251 info: "pack1 (body)" must be elaborated before "pack1 (body)"
29252 info: reason: Elaborate_All probably needed in unit "pack1 (body)"
29253 info: recompile "pack1 (body)" with -gnatwl for full details
29254 info: "pack1 (body)"
29255 info: must be elaborated along with its spec:
29256 info: "pack1 (spec)"
29257 info: which is withed by:
29258 info: "pack2 (body)"
29259 info: which must be elaborated along with its spec:
29260 info: "pack2 (spec)"
29261 info: which is withed by:
29262 info: "pack1 (body)"
29265 The sources of the circularity are the two calls to @code{Pack2.Pure} and
29266 @code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to
29267 F2 is safe, even though F2 calls F1, because the call appears after the
29268 elaboration of the body of F1. Therefore the pragma (1) is safe, and will
29269 remove the warning on the call. It is also possible to use pragma (2)
29270 because there are no other potentially unsafe calls in the block.
29273 The call to @code{Pure} is safe because this function does not depend on the
29274 state of @code{Pack2}. Therefore any call to this function is safe, and it
29275 is correct to place pragma (3) in the corresponding package spec.
29278 Finally, we could place pragma (4) in the spec of @code{Pack2} to disable
29279 warnings on all calls to functions declared therein. Note that this is not
29280 necessarily safe, and requires more detailed examination of the subprogram
29281 bodies involved. In particular, a call to @code{F2} requires that @code{F1}
29282 be already elaborated.
29286 It is hard to generalize on which of these four approaches should be
29287 taken. Obviously if it is possible to fix the program so that the default
29288 treatment works, this is preferable, but this may not always be practical.
29289 It is certainly simple enough to use
29291 but the danger in this case is that, even if the GNAT binder
29292 finds a correct elaboration order, it may not always do so,
29293 and certainly a binder from another Ada compiler might not. A
29294 combination of testing and analysis (for which the warnings generated
29297 switch can be useful) must be used to ensure that the program is free
29298 of errors. One switch that is useful in this testing is the
29299 @option{^-p (pessimistic elaboration order)^/PESSIMISTIC_ELABORATION_ORDER^}
29302 Normally the binder tries to find an order that has the best chance
29303 of avoiding elaboration problems. However, if this switch is used, the binder
29304 plays a devil's advocate role, and tries to choose the order that
29305 has the best chance of failing. If your program works even with this
29306 switch, then it has a better chance of being error free, but this is still
29309 For an example of this approach in action, consider the C-tests (executable
29310 tests) from the ACVC suite. If these are compiled and run with the default
29311 treatment, then all but one of them succeed without generating any error
29312 diagnostics from the binder. However, there is one test that fails, and
29313 this is not surprising, because the whole point of this test is to ensure
29314 that the compiler can handle cases where it is impossible to determine
29315 a correct order statically, and it checks that an exception is indeed
29316 raised at run time.
29318 This one test must be compiled and run using the
29320 switch, and then it passes. Alternatively, the entire suite can
29321 be run using this switch. It is never wrong to run with the dynamic
29322 elaboration switch if your code is correct, and we assume that the
29323 C-tests are indeed correct (it is less efficient, but efficiency is
29324 not a factor in running the ACVC tests.)
29326 @node Elaboration for Access-to-Subprogram Values
29327 @section Elaboration for Access-to-Subprogram Values
29328 @cindex Access-to-subprogram
29331 Access-to-subprogram types (introduced in Ada 95) complicate
29332 the handling of elaboration. The trouble is that it becomes
29333 impossible to tell at compile time which procedure
29334 is being called. This means that it is not possible for the binder
29335 to analyze the elaboration requirements in this case.
29337 If at the point at which the access value is created
29338 (i.e., the evaluation of @code{P'Access} for a subprogram @code{P}),
29339 the body of the subprogram is
29340 known to have been elaborated, then the access value is safe, and its use
29341 does not require a check. This may be achieved by appropriate arrangement
29342 of the order of declarations if the subprogram is in the current unit,
29343 or, if the subprogram is in another unit, by using pragma
29344 @code{Pure}, @code{Preelaborate}, or @code{Elaborate_Body}
29345 on the referenced unit.
29347 If the referenced body is not known to have been elaborated at the point
29348 the access value is created, then any use of the access value must do a
29349 dynamic check, and this dynamic check will fail and raise a
29350 @code{Program_Error} exception if the body has not been elaborated yet.
29351 GNAT will generate the necessary checks, and in addition, if the
29353 switch is set, will generate warnings that such checks are required.
29355 The use of dynamic dispatching for tagged types similarly generates
29356 a requirement for dynamic checks, and premature calls to any primitive
29357 operation of a tagged type before the body of the operation has been
29358 elaborated, will result in the raising of @code{Program_Error}.
29360 @node Summary of Procedures for Elaboration Control
29361 @section Summary of Procedures for Elaboration Control
29362 @cindex Elaboration control
29365 First, compile your program with the default options, using none of
29366 the special elaboration control switches. If the binder successfully
29367 binds your program, then you can be confident that, apart from issues
29368 raised by the use of access-to-subprogram types and dynamic dispatching,
29369 the program is free of elaboration errors. If it is important that the
29370 program be portable, then use the
29372 switch to generate warnings about missing @code{Elaborate} or
29373 @code{Elaborate_All} pragmas, and supply the missing pragmas.
29375 If the program fails to bind using the default static elaboration
29376 handling, then you can fix the program to eliminate the binder
29377 message, or recompile the entire program with the
29378 @option{-gnatE} switch to generate dynamic elaboration checks,
29379 and, if you are sure there really are no elaboration problems,
29380 use a global pragma @code{Suppress (Elaboration_Check)}.
29382 @node Other Elaboration Order Considerations
29383 @section Other Elaboration Order Considerations
29385 This section has been entirely concerned with the issue of finding a valid
29386 elaboration order, as defined by the Ada Reference Manual. In a case
29387 where several elaboration orders are valid, the task is to find one
29388 of the possible valid elaboration orders (and the static model in GNAT
29389 will ensure that this is achieved).
29391 The purpose of the elaboration rules in the Ada Reference Manual is to
29392 make sure that no entity is accessed before it has been elaborated. For
29393 a subprogram, this means that the spec and body must have been elaborated
29394 before the subprogram is called. For an object, this means that the object
29395 must have been elaborated before its value is read or written. A violation
29396 of either of these two requirements is an access before elaboration order,
29397 and this section has been all about avoiding such errors.
29399 In the case where more than one order of elaboration is possible, in the
29400 sense that access before elaboration errors are avoided, then any one of
29401 the orders is ``correct'' in the sense that it meets the requirements of
29402 the Ada Reference Manual, and no such error occurs.
29404 However, it may be the case for a given program, that there are
29405 constraints on the order of elaboration that come not from consideration
29406 of avoiding elaboration errors, but rather from extra-lingual logic
29407 requirements. Consider this example:
29409 @smallexample @c ada
29410 with Init_Constants;
29411 package Constants is
29416 package Init_Constants is
29417 procedure P; -- require a body
29418 end Init_Constants;
29421 package body Init_Constants is
29422 procedure P is begin null; end;
29426 end Init_Constants;
29430 Z : Integer := Constants.X + Constants.Y;
29434 with Text_IO; use Text_IO;
29437 Put_Line (Calc.Z'Img);
29442 In this example, there is more than one valid order of elaboration. For
29443 example both the following are correct orders:
29446 Init_Constants spec
29449 Init_Constants body
29454 Init_Constants spec
29455 Init_Constants body
29462 There is no language rule to prefer one or the other, both are correct
29463 from an order of elaboration point of view. But the programmatic effects
29464 of the two orders are very different. In the first, the elaboration routine
29465 of @code{Calc} initializes @code{Z} to zero, and then the main program
29466 runs with this value of zero. But in the second order, the elaboration
29467 routine of @code{Calc} runs after the body of Init_Constants has set
29468 @code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main}
29471 One could perhaps by applying pretty clever non-artificial intelligence
29472 to the situation guess that it is more likely that the second order of
29473 elaboration is the one desired, but there is no formal linguistic reason
29474 to prefer one over the other. In fact in this particular case, GNAT will
29475 prefer the second order, because of the rule that bodies are elaborated
29476 as soon as possible, but it's just luck that this is what was wanted
29477 (if indeed the second order was preferred).
29479 If the program cares about the order of elaboration routines in a case like
29480 this, it is important to specify the order required. In this particular
29481 case, that could have been achieved by adding to the spec of Calc:
29483 @smallexample @c ada
29484 pragma Elaborate_All (Constants);
29488 which requires that the body (if any) and spec of @code{Constants},
29489 as well as the body and spec of any unit @code{with}'ed by
29490 @code{Constants} be elaborated before @code{Calc} is elaborated.
29492 Clearly no automatic method can always guess which alternative you require,
29493 and if you are working with legacy code that had constraints of this kind
29494 which were not properly specified by adding @code{Elaborate} or
29495 @code{Elaborate_All} pragmas, then indeed it is possible that two different
29496 compilers can choose different orders.
29498 However, GNAT does attempt to diagnose the common situation where there
29499 are uninitialized variables in the visible part of a package spec, and the
29500 corresponding package body has an elaboration block that directly or
29501 indirectly initialized one or more of these variables. This is the situation
29502 in which a pragma Elaborate_Body is usually desirable, and GNAT will generate
29503 a warning that suggests this addition if it detects this situation.
29505 The @code{gnatbind}
29506 @option{^-p^/PESSIMISTIC_ELABORATION^} switch may be useful in smoking
29507 out problems. This switch causes bodies to be elaborated as late as possible
29508 instead of as early as possible. In the example above, it would have forced
29509 the choice of the first elaboration order. If you get different results
29510 when using this switch, and particularly if one set of results is right,
29511 and one is wrong as far as you are concerned, it shows that you have some
29512 missing @code{Elaborate} pragmas. For the example above, we have the
29516 gnatmake -f -q main
29519 gnatmake -f -q main -bargs -p
29525 It is of course quite unlikely that both these results are correct, so
29526 it is up to you in a case like this to investigate the source of the
29527 difference, by looking at the two elaboration orders that are chosen,
29528 and figuring out which is correct, and then adding the necessary
29529 @code{Elaborate} or @code{Elaborate_All} pragmas to ensure the desired order.
29533 @c *******************************
29534 @node Conditional Compilation
29535 @appendix Conditional Compilation
29536 @c *******************************
29537 @cindex Conditional compilation
29540 It is often necessary to arrange for a single source program
29541 to serve multiple purposes, where it is compiled in different
29542 ways to achieve these different goals. Some examples of the
29543 need for this feature are
29546 @item Adapting a program to a different hardware environment
29547 @item Adapting a program to a different target architecture
29548 @item Turning debugging features on and off
29549 @item Arranging for a program to compile with different compilers
29553 In C, or C++, the typical approach would be to use the preprocessor
29554 that is defined as part of the language. The Ada language does not
29555 contain such a feature. This is not an oversight, but rather a very
29556 deliberate design decision, based on the experience that overuse of
29557 the preprocessing features in C and C++ can result in programs that
29558 are extremely difficult to maintain. For example, if we have ten
29559 switches that can be on or off, this means that there are a thousand
29560 separate programs, any one of which might not even be syntactically
29561 correct, and even if syntactically correct, the resulting program
29562 might not work correctly. Testing all combinations can quickly become
29565 Nevertheless, the need to tailor programs certainly exists, and in
29566 this Appendix we will discuss how this can
29567 be achieved using Ada in general, and GNAT in particular.
29570 * Use of Boolean Constants::
29571 * Debugging - A Special Case::
29572 * Conditionalizing Declarations::
29573 * Use of Alternative Implementations::
29577 @node Use of Boolean Constants
29578 @section Use of Boolean Constants
29581 In the case where the difference is simply which code
29582 sequence is executed, the cleanest solution is to use Boolean
29583 constants to control which code is executed.
29585 @smallexample @c ada
29587 FP_Initialize_Required : constant Boolean := True;
29589 if FP_Initialize_Required then
29596 Not only will the code inside the @code{if} statement not be executed if
29597 the constant Boolean is @code{False}, but it will also be completely
29598 deleted from the program.
29599 However, the code is only deleted after the @code{if} statement
29600 has been checked for syntactic and semantic correctness.
29601 (In contrast, with preprocessors the code is deleted before the
29602 compiler ever gets to see it, so it is not checked until the switch
29604 @cindex Preprocessors (contrasted with conditional compilation)
29606 Typically the Boolean constants will be in a separate package,
29609 @smallexample @c ada
29612 FP_Initialize_Required : constant Boolean := True;
29613 Reset_Available : constant Boolean := False;
29620 The @code{Config} package exists in multiple forms for the various targets,
29621 with an appropriate script selecting the version of @code{Config} needed.
29622 Then any other unit requiring conditional compilation can do a @code{with}
29623 of @code{Config} to make the constants visible.
29626 @node Debugging - A Special Case
29627 @section Debugging - A Special Case
29630 A common use of conditional code is to execute statements (for example
29631 dynamic checks, or output of intermediate results) under control of a
29632 debug switch, so that the debugging behavior can be turned on and off.
29633 This can be done using a Boolean constant to control whether the code
29636 @smallexample @c ada
29639 Put_Line ("got to the first stage!");
29647 @smallexample @c ada
29649 if Debugging and then Temperature > 999.0 then
29650 raise Temperature_Crazy;
29656 Since this is a common case, there are special features to deal with
29657 this in a convenient manner. For the case of tests, Ada 2005 has added
29658 a pragma @code{Assert} that can be used for such tests. This pragma is modeled
29659 @cindex pragma @code{Assert}
29660 on the @code{Assert} pragma that has always been available in GNAT, so this
29661 feature may be used with GNAT even if you are not using Ada 2005 features.
29662 The use of pragma @code{Assert} is described in
29663 @ref{Pragma Assert,,, gnat_rm, GNAT Reference Manual}, but as an
29664 example, the last test could be written:
29666 @smallexample @c ada
29667 pragma Assert (Temperature <= 999.0, "Temperature Crazy");
29673 @smallexample @c ada
29674 pragma Assert (Temperature <= 999.0);
29678 In both cases, if assertions are active and the temperature is excessive,
29679 the exception @code{Assert_Failure} will be raised, with the given string in
29680 the first case or a string indicating the location of the pragma in the second
29681 case used as the exception message.
29683 You can turn assertions on and off by using the @code{Assertion_Policy}
29685 @cindex pragma @code{Assertion_Policy}
29686 This is an Ada 2005 pragma which is implemented in all modes by
29687 GNAT, but only in the latest versions of GNAT which include Ada 2005
29688 capability. Alternatively, you can use the @option{-gnata} switch
29689 @cindex @option{-gnata} switch
29690 to enable assertions from the command line (this is recognized by all versions
29693 For the example above with the @code{Put_Line}, the GNAT-specific pragma
29694 @code{Debug} can be used:
29695 @cindex pragma @code{Debug}
29697 @smallexample @c ada
29698 pragma Debug (Put_Line ("got to the first stage!"));
29702 If debug pragmas are enabled, the argument, which must be of the form of
29703 a procedure call, is executed (in this case, @code{Put_Line} will be called).
29704 Only one call can be present, but of course a special debugging procedure
29705 containing any code you like can be included in the program and then
29706 called in a pragma @code{Debug} argument as needed.
29708 One advantage of pragma @code{Debug} over the @code{if Debugging then}
29709 construct is that pragma @code{Debug} can appear in declarative contexts,
29710 such as at the very beginning of a procedure, before local declarations have
29713 Debug pragmas are enabled using either the @option{-gnata} switch that also
29714 controls assertions, or with a separate Debug_Policy pragma.
29715 @cindex pragma @code{Debug_Policy}
29716 The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used
29717 in Ada 95 and Ada 83 programs as well), and is analogous to
29718 pragma @code{Assertion_Policy} to control assertions.
29720 @code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas,
29721 and thus they can appear in @file{gnat.adc} if you are not using a
29722 project file, or in the file designated to contain configuration pragmas
29724 They then apply to all subsequent compilations. In practice the use of
29725 the @option{-gnata} switch is often the most convenient method of controlling
29726 the status of these pragmas.
29728 Note that a pragma is not a statement, so in contexts where a statement
29729 sequence is required, you can't just write a pragma on its own. You have
29730 to add a @code{null} statement.
29732 @smallexample @c ada
29735 @dots{} -- some statements
29737 pragma Assert (Num_Cases < 10);
29744 @node Conditionalizing Declarations
29745 @section Conditionalizing Declarations
29748 In some cases, it may be necessary to conditionalize declarations to meet
29749 different requirements. For example we might want a bit string whose length
29750 is set to meet some hardware message requirement.
29752 In some cases, it may be possible to do this using declare blocks controlled
29753 by conditional constants:
29755 @smallexample @c ada
29757 if Small_Machine then
29759 X : Bit_String (1 .. 10);
29765 X : Large_Bit_String (1 .. 1000);
29774 Note that in this approach, both declarations are analyzed by the
29775 compiler so this can only be used where both declarations are legal,
29776 even though one of them will not be used.
29778 Another approach is to define integer constants, e.g.@: @code{Bits_Per_Word}, or
29779 Boolean constants, e.g.@: @code{Little_Endian}, and then write declarations
29780 that are parameterized by these constants. For example
29782 @smallexample @c ada
29785 Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word;
29791 If @code{Bits_Per_Word} is set to 32, this generates either
29793 @smallexample @c ada
29796 Field1 at 0 range 0 .. 32;
29802 for the big endian case, or
29804 @smallexample @c ada
29807 Field1 at 0 range 10 .. 32;
29813 for the little endian case. Since a powerful subset of Ada expression
29814 notation is usable for creating static constants, clever use of this
29815 feature can often solve quite difficult problems in conditionalizing
29816 compilation (note incidentally that in Ada 95, the little endian
29817 constant was introduced as @code{System.Default_Bit_Order}, so you do not
29818 need to define this one yourself).
29821 @node Use of Alternative Implementations
29822 @section Use of Alternative Implementations
29825 In some cases, none of the approaches described above are adequate. This
29826 can occur for example if the set of declarations required is radically
29827 different for two different configurations.
29829 In this situation, the official Ada way of dealing with conditionalizing
29830 such code is to write separate units for the different cases. As long as
29831 this does not result in excessive duplication of code, this can be done
29832 without creating maintenance problems. The approach is to share common
29833 code as far as possible, and then isolate the code and declarations
29834 that are different. Subunits are often a convenient method for breaking
29835 out a piece of a unit that is to be conditionalized, with separate files
29836 for different versions of the subunit for different targets, where the
29837 build script selects the right one to give to the compiler.
29838 @cindex Subunits (and conditional compilation)
29840 As an example, consider a situation where a new feature in Ada 2005
29841 allows something to be done in a really nice way. But your code must be able
29842 to compile with an Ada 95 compiler. Conceptually you want to say:
29844 @smallexample @c ada
29847 @dots{} neat Ada 2005 code
29849 @dots{} not quite as neat Ada 95 code
29855 where @code{Ada_2005} is a Boolean constant.
29857 But this won't work when @code{Ada_2005} is set to @code{False},
29858 since the @code{then} clause will be illegal for an Ada 95 compiler.
29859 (Recall that although such unreachable code would eventually be deleted
29860 by the compiler, it still needs to be legal. If it uses features
29861 introduced in Ada 2005, it will be illegal in Ada 95.)
29863 So instead we write
29865 @smallexample @c ada
29866 procedure Insert is separate;
29870 Then we have two files for the subunit @code{Insert}, with the two sets of
29872 If the package containing this is called @code{File_Queries}, then we might
29876 @item @file{file_queries-insert-2005.adb}
29877 @item @file{file_queries-insert-95.adb}
29881 and the build script renames the appropriate file to
29884 file_queries-insert.adb
29888 and then carries out the compilation.
29890 This can also be done with project files' naming schemes. For example:
29892 @smallexample @c project
29893 For Body ("File_Queries.Insert") use "file_queries-insert-2005.ada";
29897 Note also that with project files it is desirable to use a different extension
29898 than @file{ads} / @file{adb} for alternative versions. Otherwise a naming
29899 conflict may arise through another commonly used feature: to declare as part
29900 of the project a set of directories containing all the sources obeying the
29901 default naming scheme.
29903 The use of alternative units is certainly feasible in all situations,
29904 and for example the Ada part of the GNAT run-time is conditionalized
29905 based on the target architecture using this approach. As a specific example,
29906 consider the implementation of the AST feature in VMS. There is one
29914 which is the same for all architectures, and three bodies:
29918 used for all non-VMS operating systems
29919 @item s-asthan-vms-alpha.adb
29920 used for VMS on the Alpha
29921 @item s-asthan-vms-ia64.adb
29922 used for VMS on the ia64
29926 The dummy version @file{s-asthan.adb} simply raises exceptions noting that
29927 this operating system feature is not available, and the two remaining
29928 versions interface with the corresponding versions of VMS to provide
29929 VMS-compatible AST handling. The GNAT build script knows the architecture
29930 and operating system, and automatically selects the right version,
29931 renaming it if necessary to @file{s-asthan.adb} before the run-time build.
29933 Another style for arranging alternative implementations is through Ada's
29934 access-to-subprogram facility.
29935 In case some functionality is to be conditionally included,
29936 you can declare an access-to-procedure variable @code{Ref} that is initialized
29937 to designate a ``do nothing'' procedure, and then invoke @code{Ref.all}
29939 In some library package, set @code{Ref} to @code{Proc'Access} for some
29940 procedure @code{Proc} that performs the relevant processing.
29941 The initialization only occurs if the library package is included in the
29943 The same idea can also be implemented using tagged types and dispatching
29947 @node Preprocessing
29948 @section Preprocessing
29949 @cindex Preprocessing
29952 Although it is quite possible to conditionalize code without the use of
29953 C-style preprocessing, as described earlier in this section, it is
29954 nevertheless convenient in some cases to use the C approach. Moreover,
29955 older Ada compilers have often provided some preprocessing capability,
29956 so legacy code may depend on this approach, even though it is not
29959 To accommodate such use, GNAT provides a preprocessor (modeled to a large
29960 extent on the various preprocessors that have been used
29961 with legacy code on other compilers, to enable easier transition).
29963 The preprocessor may be used in two separate modes. It can be used quite
29964 separately from the compiler, to generate a separate output source file
29965 that is then fed to the compiler as a separate step. This is the
29966 @code{gnatprep} utility, whose use is fully described in
29967 @ref{Preprocessing Using gnatprep}.
29968 @cindex @code{gnatprep}
29970 The preprocessing language allows such constructs as
29974 #if DEBUG or PRIORITY > 4 then
29975 bunch of declarations
29977 completely different bunch of declarations
29983 The values of the symbols @code{DEBUG} and @code{PRIORITY} can be
29984 defined either on the command line or in a separate file.
29986 The other way of running the preprocessor is even closer to the C style and
29987 often more convenient. In this approach the preprocessing is integrated into
29988 the compilation process. The compiler is fed the preprocessor input which
29989 includes @code{#if} lines etc, and then the compiler carries out the
29990 preprocessing internally and processes the resulting output.
29991 For more details on this approach, see @ref{Integrated Preprocessing}.
29994 @c *******************************
29995 @node Inline Assembler
29996 @appendix Inline Assembler
29997 @c *******************************
30000 If you need to write low-level software that interacts directly
30001 with the hardware, Ada provides two ways to incorporate assembly
30002 language code into your program. First, you can import and invoke
30003 external routines written in assembly language, an Ada feature fully
30004 supported by GNAT@. However, for small sections of code it may be simpler
30005 or more efficient to include assembly language statements directly
30006 in your Ada source program, using the facilities of the implementation-defined
30007 package @code{System.Machine_Code}, which incorporates the gcc
30008 Inline Assembler. The Inline Assembler approach offers a number of advantages,
30009 including the following:
30012 @item No need to use non-Ada tools
30013 @item Consistent interface over different targets
30014 @item Automatic usage of the proper calling conventions
30015 @item Access to Ada constants and variables
30016 @item Definition of intrinsic routines
30017 @item Possibility of inlining a subprogram comprising assembler code
30018 @item Code optimizer can take Inline Assembler code into account
30021 This chapter presents a series of examples to show you how to use
30022 the Inline Assembler. Although it focuses on the Intel x86,
30023 the general approach applies also to other processors.
30024 It is assumed that you are familiar with Ada
30025 and with assembly language programming.
30028 * Basic Assembler Syntax::
30029 * A Simple Example of Inline Assembler::
30030 * Output Variables in Inline Assembler::
30031 * Input Variables in Inline Assembler::
30032 * Inlining Inline Assembler Code::
30033 * Other Asm Functionality::
30036 @c ---------------------------------------------------------------------------
30037 @node Basic Assembler Syntax
30038 @section Basic Assembler Syntax
30041 The assembler used by GNAT and gcc is based not on the Intel assembly
30042 language, but rather on a language that descends from the AT&T Unix
30043 assembler @emph{as} (and which is often referred to as ``AT&T syntax'').
30044 The following table summarizes the main features of @emph{as} syntax
30045 and points out the differences from the Intel conventions.
30046 See the gcc @emph{as} and @emph{gas} (an @emph{as} macro
30047 pre-processor) documentation for further information.
30050 @item Register names
30051 gcc / @emph{as}: Prefix with ``%''; for example @code{%eax}
30053 Intel: No extra punctuation; for example @code{eax}
30055 @item Immediate operand
30056 gcc / @emph{as}: Prefix with ``$''; for example @code{$4}
30058 Intel: No extra punctuation; for example @code{4}
30061 gcc / @emph{as}: Prefix with ``$''; for example @code{$loc}
30063 Intel: No extra punctuation; for example @code{loc}
30065 @item Memory contents
30066 gcc / @emph{as}: No extra punctuation; for example @code{loc}
30068 Intel: Square brackets; for example @code{[loc]}
30070 @item Register contents
30071 gcc / @emph{as}: Parentheses; for example @code{(%eax)}
30073 Intel: Square brackets; for example @code{[eax]}
30075 @item Hexadecimal numbers
30076 gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0}
30078 Intel: Trailing ``h''; for example @code{A0h}
30081 gcc / @emph{as}: Explicit in op code; for example @code{movw} to move
30084 Intel: Implicit, deduced by assembler; for example @code{mov}
30086 @item Instruction repetition
30087 gcc / @emph{as}: Split into two lines; for example
30093 Intel: Keep on one line; for example @code{rep stosl}
30095 @item Order of operands
30096 gcc / @emph{as}: Source first; for example @code{movw $4, %eax}
30098 Intel: Destination first; for example @code{mov eax, 4}
30101 @c ---------------------------------------------------------------------------
30102 @node A Simple Example of Inline Assembler
30103 @section A Simple Example of Inline Assembler
30106 The following example will generate a single assembly language statement,
30107 @code{nop}, which does nothing. Despite its lack of run-time effect,
30108 the example will be useful in illustrating the basics of
30109 the Inline Assembler facility.
30111 @smallexample @c ada
30113 with System.Machine_Code; use System.Machine_Code;
30114 procedure Nothing is
30121 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
30122 here it takes one parameter, a @emph{template string} that must be a static
30123 expression and that will form the generated instruction.
30124 @code{Asm} may be regarded as a compile-time procedure that parses
30125 the template string and additional parameters (none here),
30126 from which it generates a sequence of assembly language instructions.
30128 The examples in this chapter will illustrate several of the forms
30129 for invoking @code{Asm}; a complete specification of the syntax
30130 is found in @ref{Machine Code Insertions,,, gnat_rm, GNAT Reference
30133 Under the standard GNAT conventions, the @code{Nothing} procedure
30134 should be in a file named @file{nothing.adb}.
30135 You can build the executable in the usual way:
30139 However, the interesting aspect of this example is not its run-time behavior
30140 but rather the generated assembly code.
30141 To see this output, invoke the compiler as follows:
30143 gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb}
30145 where the options are:
30149 compile only (no bind or link)
30151 generate assembler listing
30152 @item -fomit-frame-pointer
30153 do not set up separate stack frames
30155 do not add runtime checks
30158 This gives a human-readable assembler version of the code. The resulting
30159 file will have the same name as the Ada source file, but with a @code{.s}
30160 extension. In our example, the file @file{nothing.s} has the following
30165 .file "nothing.adb"
30167 ___gnu_compiled_ada:
30170 .globl __ada_nothing
30182 The assembly code you included is clearly indicated by
30183 the compiler, between the @code{#APP} and @code{#NO_APP}
30184 delimiters. The character before the 'APP' and 'NOAPP'
30185 can differ on different targets. For example, GNU/Linux uses '#APP' while
30186 on NT you will see '/APP'.
30188 If you make a mistake in your assembler code (such as using the
30189 wrong size modifier, or using a wrong operand for the instruction) GNAT
30190 will report this error in a temporary file, which will be deleted when
30191 the compilation is finished. Generating an assembler file will help
30192 in such cases, since you can assemble this file separately using the
30193 @emph{as} assembler that comes with gcc.
30195 Assembling the file using the command
30198 as @file{nothing.s}
30201 will give you error messages whose lines correspond to the assembler
30202 input file, so you can easily find and correct any mistakes you made.
30203 If there are no errors, @emph{as} will generate an object file
30204 @file{nothing.out}.
30206 @c ---------------------------------------------------------------------------
30207 @node Output Variables in Inline Assembler
30208 @section Output Variables in Inline Assembler
30211 The examples in this section, showing how to access the processor flags,
30212 illustrate how to specify the destination operands for assembly language
30215 @smallexample @c ada
30217 with Interfaces; use Interfaces;
30218 with Ada.Text_IO; use Ada.Text_IO;
30219 with System.Machine_Code; use System.Machine_Code;
30220 procedure Get_Flags is
30221 Flags : Unsigned_32;
30224 Asm ("pushfl" & LF & HT & -- push flags on stack
30225 "popl %%eax" & LF & HT & -- load eax with flags
30226 "movl %%eax, %0", -- store flags in variable
30227 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30228 Put_Line ("Flags register:" & Flags'Img);
30233 In order to have a nicely aligned assembly listing, we have separated
30234 multiple assembler statements in the Asm template string with linefeed
30235 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
30236 The resulting section of the assembly output file is:
30243 movl %eax, -40(%ebp)
30248 It would have been legal to write the Asm invocation as:
30251 Asm ("pushfl popl %%eax movl %%eax, %0")
30254 but in the generated assembler file, this would come out as:
30258 pushfl popl %eax movl %eax, -40(%ebp)
30262 which is not so convenient for the human reader.
30264 We use Ada comments
30265 at the end of each line to explain what the assembler instructions
30266 actually do. This is a useful convention.
30268 When writing Inline Assembler instructions, you need to precede each register
30269 and variable name with a percent sign. Since the assembler already requires
30270 a percent sign at the beginning of a register name, you need two consecutive
30271 percent signs for such names in the Asm template string, thus @code{%%eax}.
30272 In the generated assembly code, one of the percent signs will be stripped off.
30274 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
30275 variables: operands you later define using @code{Input} or @code{Output}
30276 parameters to @code{Asm}.
30277 An output variable is illustrated in
30278 the third statement in the Asm template string:
30282 The intent is to store the contents of the eax register in a variable that can
30283 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
30284 necessarily work, since the compiler might optimize by using a register
30285 to hold Flags, and the expansion of the @code{movl} instruction would not be
30286 aware of this optimization. The solution is not to store the result directly
30287 but rather to advise the compiler to choose the correct operand form;
30288 that is the purpose of the @code{%0} output variable.
30290 Information about the output variable is supplied in the @code{Outputs}
30291 parameter to @code{Asm}:
30293 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30296 The output is defined by the @code{Asm_Output} attribute of the target type;
30297 the general format is
30299 Type'Asm_Output (constraint_string, variable_name)
30302 The constraint string directs the compiler how
30303 to store/access the associated variable. In the example
30305 Unsigned_32'Asm_Output ("=m", Flags);
30307 the @code{"m"} (memory) constraint tells the compiler that the variable
30308 @code{Flags} should be stored in a memory variable, thus preventing
30309 the optimizer from keeping it in a register. In contrast,
30311 Unsigned_32'Asm_Output ("=r", Flags);
30313 uses the @code{"r"} (register) constraint, telling the compiler to
30314 store the variable in a register.
30316 If the constraint is preceded by the equal character (@strong{=}), it tells
30317 the compiler that the variable will be used to store data into it.
30319 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
30320 allowing the optimizer to choose whatever it deems best.
30322 There are a fairly large number of constraints, but the ones that are
30323 most useful (for the Intel x86 processor) are the following:
30329 global (i.e.@: can be stored anywhere)
30347 use one of eax, ebx, ecx or edx
30349 use one of eax, ebx, ecx, edx, esi or edi
30352 The full set of constraints is described in the gcc and @emph{as}
30353 documentation; note that it is possible to combine certain constraints
30354 in one constraint string.
30356 You specify the association of an output variable with an assembler operand
30357 through the @code{%}@emph{n} notation, where @emph{n} is a non-negative
30359 @smallexample @c ada
30361 Asm ("pushfl" & LF & HT & -- push flags on stack
30362 "popl %%eax" & LF & HT & -- load eax with flags
30363 "movl %%eax, %0", -- store flags in variable
30364 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30368 @code{%0} will be replaced in the expanded code by the appropriate operand,
30370 the compiler decided for the @code{Flags} variable.
30372 In general, you may have any number of output variables:
30375 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
30377 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
30378 of @code{Asm_Output} attributes
30382 @smallexample @c ada
30384 Asm ("movl %%eax, %0" & LF & HT &
30385 "movl %%ebx, %1" & LF & HT &
30387 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
30388 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
30389 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
30393 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
30394 in the Ada program.
30396 As a variation on the @code{Get_Flags} example, we can use the constraints
30397 string to direct the compiler to store the eax register into the @code{Flags}
30398 variable, instead of including the store instruction explicitly in the
30399 @code{Asm} template string:
30401 @smallexample @c ada
30403 with Interfaces; use Interfaces;
30404 with Ada.Text_IO; use Ada.Text_IO;
30405 with System.Machine_Code; use System.Machine_Code;
30406 procedure Get_Flags_2 is
30407 Flags : Unsigned_32;
30410 Asm ("pushfl" & LF & HT & -- push flags on stack
30411 "popl %%eax", -- save flags in eax
30412 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
30413 Put_Line ("Flags register:" & Flags'Img);
30419 The @code{"a"} constraint tells the compiler that the @code{Flags}
30420 variable will come from the eax register. Here is the resulting code:
30428 movl %eax,-40(%ebp)
30433 The compiler generated the store of eax into Flags after
30434 expanding the assembler code.
30436 Actually, there was no need to pop the flags into the eax register;
30437 more simply, we could just pop the flags directly into the program variable:
30439 @smallexample @c ada
30441 with Interfaces; use Interfaces;
30442 with Ada.Text_IO; use Ada.Text_IO;
30443 with System.Machine_Code; use System.Machine_Code;
30444 procedure Get_Flags_3 is
30445 Flags : Unsigned_32;
30448 Asm ("pushfl" & LF & HT & -- push flags on stack
30449 "pop %0", -- save flags in Flags
30450 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30451 Put_Line ("Flags register:" & Flags'Img);
30456 @c ---------------------------------------------------------------------------
30457 @node Input Variables in Inline Assembler
30458 @section Input Variables in Inline Assembler
30461 The example in this section illustrates how to specify the source operands
30462 for assembly language statements.
30463 The program simply increments its input value by 1:
30465 @smallexample @c ada
30467 with Interfaces; use Interfaces;
30468 with Ada.Text_IO; use Ada.Text_IO;
30469 with System.Machine_Code; use System.Machine_Code;
30470 procedure Increment is
30472 function Incr (Value : Unsigned_32) return Unsigned_32 is
30473 Result : Unsigned_32;
30476 Inputs => Unsigned_32'Asm_Input ("a", Value),
30477 Outputs => Unsigned_32'Asm_Output ("=a", Result));
30481 Value : Unsigned_32;
30485 Put_Line ("Value before is" & Value'Img);
30486 Value := Incr (Value);
30487 Put_Line ("Value after is" & Value'Img);
30492 The @code{Outputs} parameter to @code{Asm} specifies
30493 that the result will be in the eax register and that it is to be stored
30494 in the @code{Result} variable.
30496 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
30497 but with an @code{Asm_Input} attribute.
30498 The @code{"="} constraint, indicating an output value, is not present.
30500 You can have multiple input variables, in the same way that you can have more
30501 than one output variable.
30503 The parameter count (%0, %1) etc, now starts at the first input
30504 statement, and continues with the output statements.
30505 When both parameters use the same variable, the
30506 compiler will treat them as the same %n operand, which is the case here.
30508 Just as the @code{Outputs} parameter causes the register to be stored into the
30509 target variable after execution of the assembler statements, so does the
30510 @code{Inputs} parameter cause its variable to be loaded into the register
30511 before execution of the assembler statements.
30513 Thus the effect of the @code{Asm} invocation is:
30515 @item load the 32-bit value of @code{Value} into eax
30516 @item execute the @code{incl %eax} instruction
30517 @item store the contents of eax into the @code{Result} variable
30520 The resulting assembler file (with @option{-O2} optimization) contains:
30523 _increment__incr.1:
30536 @c ---------------------------------------------------------------------------
30537 @node Inlining Inline Assembler Code
30538 @section Inlining Inline Assembler Code
30541 For a short subprogram such as the @code{Incr} function in the previous
30542 section, the overhead of the call and return (creating / deleting the stack
30543 frame) can be significant, compared to the amount of code in the subprogram
30544 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
30545 which directs the compiler to expand invocations of the subprogram at the
30546 point(s) of call, instead of setting up a stack frame for out-of-line calls.
30547 Here is the resulting program:
30549 @smallexample @c ada
30551 with Interfaces; use Interfaces;
30552 with Ada.Text_IO; use Ada.Text_IO;
30553 with System.Machine_Code; use System.Machine_Code;
30554 procedure Increment_2 is
30556 function Incr (Value : Unsigned_32) return Unsigned_32 is
30557 Result : Unsigned_32;
30560 Inputs => Unsigned_32'Asm_Input ("a", Value),
30561 Outputs => Unsigned_32'Asm_Output ("=a", Result));
30564 pragma Inline (Increment);
30566 Value : Unsigned_32;
30570 Put_Line ("Value before is" & Value'Img);
30571 Value := Increment (Value);
30572 Put_Line ("Value after is" & Value'Img);
30577 Compile the program with both optimization (@option{-O2}) and inlining
30578 (@option{-gnatn}) enabled.
30580 The @code{Incr} function is still compiled as usual, but at the
30581 point in @code{Increment} where our function used to be called:
30586 call _increment__incr.1
30591 the code for the function body directly appears:
30604 thus saving the overhead of stack frame setup and an out-of-line call.
30606 @c ---------------------------------------------------------------------------
30607 @node Other Asm Functionality
30608 @section Other @code{Asm} Functionality
30611 This section describes two important parameters to the @code{Asm}
30612 procedure: @code{Clobber}, which identifies register usage;
30613 and @code{Volatile}, which inhibits unwanted optimizations.
30616 * The Clobber Parameter::
30617 * The Volatile Parameter::
30620 @c ---------------------------------------------------------------------------
30621 @node The Clobber Parameter
30622 @subsection The @code{Clobber} Parameter
30625 One of the dangers of intermixing assembly language and a compiled language
30626 such as Ada is that the compiler needs to be aware of which registers are
30627 being used by the assembly code. In some cases, such as the earlier examples,
30628 the constraint string is sufficient to indicate register usage (e.g.,
30630 the eax register). But more generally, the compiler needs an explicit
30631 identification of the registers that are used by the Inline Assembly
30634 Using a register that the compiler doesn't know about
30635 could be a side effect of an instruction (like @code{mull}
30636 storing its result in both eax and edx).
30637 It can also arise from explicit register usage in your
30638 assembly code; for example:
30641 Asm ("movl %0, %%ebx" & LF & HT &
30643 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30644 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out));
30648 where the compiler (since it does not analyze the @code{Asm} template string)
30649 does not know you are using the ebx register.
30651 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
30652 to identify the registers that will be used by your assembly code:
30656 Asm ("movl %0, %%ebx" & LF & HT &
30658 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30659 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30664 The Clobber parameter is a static string expression specifying the
30665 register(s) you are using. Note that register names are @emph{not} prefixed
30666 by a percent sign. Also, if more than one register is used then their names
30667 are separated by commas; e.g., @code{"eax, ebx"}
30669 The @code{Clobber} parameter has several additional uses:
30671 @item Use ``register'' name @code{cc} to indicate that flags might have changed
30672 @item Use ``register'' name @code{memory} if you changed a memory location
30675 @c ---------------------------------------------------------------------------
30676 @node The Volatile Parameter
30677 @subsection The @code{Volatile} Parameter
30678 @cindex Volatile parameter
30681 Compiler optimizations in the presence of Inline Assembler may sometimes have
30682 unwanted effects. For example, when an @code{Asm} invocation with an input
30683 variable is inside a loop, the compiler might move the loading of the input
30684 variable outside the loop, regarding it as a one-time initialization.
30686 If this effect is not desired, you can disable such optimizations by setting
30687 the @code{Volatile} parameter to @code{True}; for example:
30689 @smallexample @c ada
30691 Asm ("movl %0, %%ebx" & LF & HT &
30693 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30694 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30700 By default, @code{Volatile} is set to @code{False} unless there is no
30701 @code{Outputs} parameter.
30703 Although setting @code{Volatile} to @code{True} prevents unwanted
30704 optimizations, it will also disable other optimizations that might be
30705 important for efficiency. In general, you should set @code{Volatile}
30706 to @code{True} only if the compiler's optimizations have created
30708 @c END OF INLINE ASSEMBLER CHAPTER
30709 @c ===============================
30711 @c ***********************************
30712 @c * Compatibility and Porting Guide *
30713 @c ***********************************
30714 @node Compatibility and Porting Guide
30715 @appendix Compatibility and Porting Guide
30718 This chapter describes the compatibility issues that may arise between
30719 GNAT and other Ada compilation systems (including those for Ada 83),
30720 and shows how GNAT can expedite porting
30721 applications developed in other Ada environments.
30724 * Compatibility with Ada 83::
30725 * Compatibility between Ada 95 and Ada 2005::
30726 * Implementation-dependent characteristics::
30727 * Compatibility with Other Ada Systems::
30728 * Representation Clauses::
30730 @c Brief section is only in non-VMS version
30731 @c Full chapter is in VMS version
30732 * Compatibility with HP Ada 83::
30735 * Transitioning to 64-Bit GNAT for OpenVMS::
30739 @node Compatibility with Ada 83
30740 @section Compatibility with Ada 83
30741 @cindex Compatibility (between Ada 83 and Ada 95 / Ada 2005)
30744 Ada 95 and Ada 2005 are highly upwards compatible with Ada 83. In
30745 particular, the design intention was that the difficulties associated
30746 with moving from Ada 83 to Ada 95 or Ada 2005 should be no greater than those
30747 that occur when moving from one Ada 83 system to another.
30749 However, there are a number of points at which there are minor
30750 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
30751 full details of these issues,
30752 and should be consulted for a complete treatment.
30754 following subsections treat the most likely issues to be encountered.
30757 * Legal Ada 83 programs that are illegal in Ada 95::
30758 * More deterministic semantics::
30759 * Changed semantics::
30760 * Other language compatibility issues::
30763 @node Legal Ada 83 programs that are illegal in Ada 95
30764 @subsection Legal Ada 83 programs that are illegal in Ada 95
30766 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
30767 Ada 95 and thus also in Ada 2005:
30770 @item Character literals
30771 Some uses of character literals are ambiguous. Since Ada 95 has introduced
30772 @code{Wide_Character} as a new predefined character type, some uses of
30773 character literals that were legal in Ada 83 are illegal in Ada 95.
30775 @smallexample @c ada
30776 for Char in 'A' .. 'Z' loop @dots{} end loop;
30780 The problem is that @code{'A'} and @code{'Z'} could be from either
30781 @code{Character} or @code{Wide_Character}. The simplest correction
30782 is to make the type explicit; e.g.:
30783 @smallexample @c ada
30784 for Char in Character range 'A' .. 'Z' loop @dots{} end loop;
30787 @item New reserved words
30788 The identifiers @code{abstract}, @code{aliased}, @code{protected},
30789 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
30790 Existing Ada 83 code using any of these identifiers must be edited to
30791 use some alternative name.
30793 @item Freezing rules
30794 The rules in Ada 95 are slightly different with regard to the point at
30795 which entities are frozen, and representation pragmas and clauses are
30796 not permitted past the freeze point. This shows up most typically in
30797 the form of an error message complaining that a representation item
30798 appears too late, and the appropriate corrective action is to move
30799 the item nearer to the declaration of the entity to which it refers.
30801 A particular case is that representation pragmas
30804 extended HP Ada 83 compatibility pragmas such as @code{Export_Procedure})
30806 cannot be applied to a subprogram body. If necessary, a separate subprogram
30807 declaration must be introduced to which the pragma can be applied.
30809 @item Optional bodies for library packages
30810 In Ada 83, a package that did not require a package body was nevertheless
30811 allowed to have one. This lead to certain surprises in compiling large
30812 systems (situations in which the body could be unexpectedly ignored by the
30813 binder). In Ada 95, if a package does not require a body then it is not
30814 permitted to have a body. To fix this problem, simply remove a redundant
30815 body if it is empty, or, if it is non-empty, introduce a dummy declaration
30816 into the spec that makes the body required. One approach is to add a private
30817 part to the package declaration (if necessary), and define a parameterless
30818 procedure called @code{Requires_Body}, which must then be given a dummy
30819 procedure body in the package body, which then becomes required.
30820 Another approach (assuming that this does not introduce elaboration
30821 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
30822 since one effect of this pragma is to require the presence of a package body.
30824 @item @code{Numeric_Error} is now the same as @code{Constraint_Error}
30825 In Ada 95, the exception @code{Numeric_Error} is a renaming of
30826 @code{Constraint_Error}.
30827 This means that it is illegal to have separate exception handlers for
30828 the two exceptions. The fix is simply to remove the handler for the
30829 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
30830 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
30832 @item Indefinite subtypes in generics
30833 In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String})
30834 as the actual for a generic formal private type, but then the instantiation
30835 would be illegal if there were any instances of declarations of variables
30836 of this type in the generic body. In Ada 95, to avoid this clear violation
30837 of the methodological principle known as the ``contract model'',
30838 the generic declaration explicitly indicates whether
30839 or not such instantiations are permitted. If a generic formal parameter
30840 has explicit unknown discriminants, indicated by using @code{(<>)} after the
30841 type name, then it can be instantiated with indefinite types, but no
30842 stand-alone variables can be declared of this type. Any attempt to declare
30843 such a variable will result in an illegality at the time the generic is
30844 declared. If the @code{(<>)} notation is not used, then it is illegal
30845 to instantiate the generic with an indefinite type.
30846 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
30847 It will show up as a compile time error, and
30848 the fix is usually simply to add the @code{(<>)} to the generic declaration.
30851 @node More deterministic semantics
30852 @subsection More deterministic semantics
30856 Conversions from real types to integer types round away from 0. In Ada 83
30857 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
30858 implementation freedom was intended to support unbiased rounding in
30859 statistical applications, but in practice it interfered with portability.
30860 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
30861 is required. Numeric code may be affected by this change in semantics.
30862 Note, though, that this issue is no worse than already existed in Ada 83
30863 when porting code from one vendor to another.
30866 The Real-Time Annex introduces a set of policies that define the behavior of
30867 features that were implementation dependent in Ada 83, such as the order in
30868 which open select branches are executed.
30871 @node Changed semantics
30872 @subsection Changed semantics
30875 The worst kind of incompatibility is one where a program that is legal in
30876 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
30877 possible in Ada 83. Fortunately this is extremely rare, but the one
30878 situation that you should be alert to is the change in the predefined type
30879 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
30882 @item Range of type @code{Character}
30883 The range of @code{Standard.Character} is now the full 256 characters
30884 of Latin-1, whereas in most Ada 83 implementations it was restricted
30885 to 128 characters. Although some of the effects of
30886 this change will be manifest in compile-time rejection of legal
30887 Ada 83 programs it is possible for a working Ada 83 program to have
30888 a different effect in Ada 95, one that was not permitted in Ada 83.
30889 As an example, the expression
30890 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
30891 delivers @code{255} as its value.
30892 In general, you should look at the logic of any
30893 character-processing Ada 83 program and see whether it needs to be adapted
30894 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
30895 character handling package that may be relevant if code needs to be adapted
30896 to account for the additional Latin-1 elements.
30897 The desirable fix is to
30898 modify the program to accommodate the full character set, but in some cases
30899 it may be convenient to define a subtype or derived type of Character that
30900 covers only the restricted range.
30904 @node Other language compatibility issues
30905 @subsection Other language compatibility issues
30908 @item @option{-gnat83} switch
30909 All implementations of GNAT provide a switch that causes GNAT to operate
30910 in Ada 83 mode. In this mode, some but not all compatibility problems
30911 of the type described above are handled automatically. For example, the
30912 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
30913 as identifiers as in Ada 83.
30915 in practice, it is usually advisable to make the necessary modifications
30916 to the program to remove the need for using this switch.
30917 See @ref{Compiling Different Versions of Ada}.
30919 @item Support for removed Ada 83 pragmas and attributes
30920 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
30921 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
30922 compilers are allowed, but not required, to implement these missing
30923 elements. In contrast with some other compilers, GNAT implements all
30924 such pragmas and attributes, eliminating this compatibility concern. These
30925 include @code{pragma Interface} and the floating point type attributes
30926 (@code{Emax}, @code{Mantissa}, etc.), among other items.
30930 @node Compatibility between Ada 95 and Ada 2005
30931 @section Compatibility between Ada 95 and Ada 2005
30932 @cindex Compatibility between Ada 95 and Ada 2005
30935 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
30936 a number of incompatibilities. Several are enumerated below;
30937 for a complete description please see the
30938 Annotated Ada 2005 Reference Manual, or section 9.1.1 in
30939 @cite{Rationale for Ada 2005}.
30942 @item New reserved words.
30943 The words @code{interface}, @code{overriding} and @code{synchronized} are
30944 reserved in Ada 2005.
30945 A pre-Ada 2005 program that uses any of these as an identifier will be
30948 @item New declarations in predefined packages.
30949 A number of packages in the predefined environment contain new declarations:
30950 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
30951 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
30952 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
30953 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
30954 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
30955 If an Ada 95 program does a @code{with} and @code{use} of any of these
30956 packages, the new declarations may cause name clashes.
30958 @item Access parameters.
30959 A nondispatching subprogram with an access parameter cannot be renamed
30960 as a dispatching operation. This was permitted in Ada 95.
30962 @item Access types, discriminants, and constraints.
30963 Rule changes in this area have led to some incompatibilities; for example,
30964 constrained subtypes of some access types are not permitted in Ada 2005.
30966 @item Aggregates for limited types.
30967 The allowance of aggregates for limited types in Ada 2005 raises the
30968 possibility of ambiguities in legal Ada 95 programs, since additional types
30969 now need to be considered in expression resolution.
30971 @item Fixed-point multiplication and division.
30972 Certain expressions involving ``*'' or ``/'' for a fixed-point type, which
30973 were legal in Ada 95 and invoked the predefined versions of these operations,
30975 The ambiguity may be resolved either by applying a type conversion to the
30976 expression, or by explicitly invoking the operation from package
30979 @item Return-by-reference types.
30980 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
30981 can declare a function returning a value from an anonymous access type.
30985 @node Implementation-dependent characteristics
30986 @section Implementation-dependent characteristics
30988 Although the Ada language defines the semantics of each construct as
30989 precisely as practical, in some situations (for example for reasons of
30990 efficiency, or where the effect is heavily dependent on the host or target
30991 platform) the implementation is allowed some freedom. In porting Ada 83
30992 code to GNAT, you need to be aware of whether / how the existing code
30993 exercised such implementation dependencies. Such characteristics fall into
30994 several categories, and GNAT offers specific support in assisting the
30995 transition from certain Ada 83 compilers.
30998 * Implementation-defined pragmas::
30999 * Implementation-defined attributes::
31001 * Elaboration order::
31002 * Target-specific aspects::
31005 @node Implementation-defined pragmas
31006 @subsection Implementation-defined pragmas
31009 Ada compilers are allowed to supplement the language-defined pragmas, and
31010 these are a potential source of non-portability. All GNAT-defined pragmas
31011 are described in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT
31012 Reference Manual}, and these include several that are specifically
31013 intended to correspond to other vendors' Ada 83 pragmas.
31014 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
31015 For compatibility with HP Ada 83, GNAT supplies the pragmas
31016 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
31017 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
31018 and @code{Volatile}.
31019 Other relevant pragmas include @code{External} and @code{Link_With}.
31020 Some vendor-specific
31021 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
31023 avoiding compiler rejection of units that contain such pragmas; they are not
31024 relevant in a GNAT context and hence are not otherwise implemented.
31026 @node Implementation-defined attributes
31027 @subsection Implementation-defined attributes
31029 Analogous to pragmas, the set of attributes may be extended by an
31030 implementation. All GNAT-defined attributes are described in
31031 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference
31032 Manual}, and these include several that are specifically intended
31033 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
31034 the attribute @code{VADS_Size} may be useful. For compatibility with HP
31035 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
31039 @subsection Libraries
31041 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
31042 code uses vendor-specific libraries then there are several ways to manage
31043 this in Ada 95 or Ada 2005:
31046 If the source code for the libraries (specs and bodies) are
31047 available, then the libraries can be migrated in the same way as the
31050 If the source code for the specs but not the bodies are
31051 available, then you can reimplement the bodies.
31053 Some features introduced by Ada 95 obviate the need for library support. For
31054 example most Ada 83 vendors supplied a package for unsigned integers. The
31055 Ada 95 modular type feature is the preferred way to handle this need, so
31056 instead of migrating or reimplementing the unsigned integer package it may
31057 be preferable to retrofit the application using modular types.
31060 @node Elaboration order
31061 @subsection Elaboration order
31063 The implementation can choose any elaboration order consistent with the unit
31064 dependency relationship. This freedom means that some orders can result in
31065 Program_Error being raised due to an ``Access Before Elaboration'': an attempt
31066 to invoke a subprogram its body has been elaborated, or to instantiate a
31067 generic before the generic body has been elaborated. By default GNAT
31068 attempts to choose a safe order (one that will not encounter access before
31069 elaboration problems) by implicitly inserting @code{Elaborate} or
31070 @code{Elaborate_All} pragmas where
31071 needed. However, this can lead to the creation of elaboration circularities
31072 and a resulting rejection of the program by gnatbind. This issue is
31073 thoroughly described in @ref{Elaboration Order Handling in GNAT}.
31074 In brief, there are several
31075 ways to deal with this situation:
31079 Modify the program to eliminate the circularities, e.g.@: by moving
31080 elaboration-time code into explicitly-invoked procedures
31082 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
31083 @code{Elaborate} pragmas, and then inhibit the generation of implicit
31084 @code{Elaborate_All}
31085 pragmas either globally (as an effect of the @option{-gnatE} switch) or locally
31086 (by selectively suppressing elaboration checks via pragma
31087 @code{Suppress(Elaboration_Check)} when it is safe to do so).
31090 @node Target-specific aspects
31091 @subsection Target-specific aspects
31093 Low-level applications need to deal with machine addresses, data
31094 representations, interfacing with assembler code, and similar issues. If
31095 such an Ada 83 application is being ported to different target hardware (for
31096 example where the byte endianness has changed) then you will need to
31097 carefully examine the program logic; the porting effort will heavily depend
31098 on the robustness of the original design. Moreover, Ada 95 (and thus
31099 Ada 2005) are sometimes
31100 incompatible with typical Ada 83 compiler practices regarding implicit
31101 packing, the meaning of the Size attribute, and the size of access values.
31102 GNAT's approach to these issues is described in @ref{Representation Clauses}.
31104 @node Compatibility with Other Ada Systems
31105 @section Compatibility with Other Ada Systems
31108 If programs avoid the use of implementation dependent and
31109 implementation defined features, as documented in the @cite{Ada
31110 Reference Manual}, there should be a high degree of portability between
31111 GNAT and other Ada systems. The following are specific items which
31112 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
31113 compilers, but do not affect porting code to GNAT@.
31114 (As of @value{NOW}, GNAT is the only compiler available for Ada 2005;
31115 the following issues may or may not arise for Ada 2005 programs
31116 when other compilers appear.)
31119 @item Ada 83 Pragmas and Attributes
31120 Ada 95 compilers are allowed, but not required, to implement the missing
31121 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
31122 GNAT implements all such pragmas and attributes, eliminating this as
31123 a compatibility concern, but some other Ada 95 compilers reject these
31124 pragmas and attributes.
31126 @item Specialized Needs Annexes
31127 GNAT implements the full set of special needs annexes. At the
31128 current time, it is the only Ada 95 compiler to do so. This means that
31129 programs making use of these features may not be portable to other Ada
31130 95 compilation systems.
31132 @item Representation Clauses
31133 Some other Ada 95 compilers implement only the minimal set of
31134 representation clauses required by the Ada 95 reference manual. GNAT goes
31135 far beyond this minimal set, as described in the next section.
31138 @node Representation Clauses
31139 @section Representation Clauses
31142 The Ada 83 reference manual was quite vague in describing both the minimal
31143 required implementation of representation clauses, and also their precise
31144 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
31145 minimal set of capabilities required is still quite limited.
31147 GNAT implements the full required set of capabilities in
31148 Ada 95 and Ada 2005, but also goes much further, and in particular
31149 an effort has been made to be compatible with existing Ada 83 usage to the
31150 greatest extent possible.
31152 A few cases exist in which Ada 83 compiler behavior is incompatible with
31153 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
31154 intentional or accidental dependence on specific implementation dependent
31155 characteristics of these Ada 83 compilers. The following is a list of
31156 the cases most likely to arise in existing Ada 83 code.
31159 @item Implicit Packing
31160 Some Ada 83 compilers allowed a Size specification to cause implicit
31161 packing of an array or record. This could cause expensive implicit
31162 conversions for change of representation in the presence of derived
31163 types, and the Ada design intends to avoid this possibility.
31164 Subsequent AI's were issued to make it clear that such implicit
31165 change of representation in response to a Size clause is inadvisable,
31166 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
31167 Reference Manuals as implementation advice that is followed by GNAT@.
31168 The problem will show up as an error
31169 message rejecting the size clause. The fix is simply to provide
31170 the explicit pragma @code{Pack}, or for more fine tuned control, provide
31171 a Component_Size clause.
31173 @item Meaning of Size Attribute
31174 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
31175 the minimal number of bits required to hold values of the type. For example,
31176 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
31177 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
31178 some 32 in this situation. This problem will usually show up as a compile
31179 time error, but not always. It is a good idea to check all uses of the
31180 'Size attribute when porting Ada 83 code. The GNAT specific attribute
31181 Object_Size can provide a useful way of duplicating the behavior of
31182 some Ada 83 compiler systems.
31184 @item Size of Access Types
31185 A common assumption in Ada 83 code is that an access type is in fact a pointer,
31186 and that therefore it will be the same size as a System.Address value. This
31187 assumption is true for GNAT in most cases with one exception. For the case of
31188 a pointer to an unconstrained array type (where the bounds may vary from one
31189 value of the access type to another), the default is to use a ``fat pointer'',
31190 which is represented as two separate pointers, one to the bounds, and one to
31191 the array. This representation has a number of advantages, including improved
31192 efficiency. However, it may cause some difficulties in porting existing Ada 83
31193 code which makes the assumption that, for example, pointers fit in 32 bits on
31194 a machine with 32-bit addressing.
31196 To get around this problem, GNAT also permits the use of ``thin pointers'' for
31197 access types in this case (where the designated type is an unconstrained array
31198 type). These thin pointers are indeed the same size as a System.Address value.
31199 To specify a thin pointer, use a size clause for the type, for example:
31201 @smallexample @c ada
31202 type X is access all String;
31203 for X'Size use Standard'Address_Size;
31207 which will cause the type X to be represented using a single pointer.
31208 When using this representation, the bounds are right behind the array.
31209 This representation is slightly less efficient, and does not allow quite
31210 such flexibility in the use of foreign pointers or in using the
31211 Unrestricted_Access attribute to create pointers to non-aliased objects.
31212 But for any standard portable use of the access type it will work in
31213 a functionally correct manner and allow porting of existing code.
31214 Note that another way of forcing a thin pointer representation
31215 is to use a component size clause for the element size in an array,
31216 or a record representation clause for an access field in a record.
31220 @c This brief section is only in the non-VMS version
31221 @c The complete chapter on HP Ada is in the VMS version
31222 @node Compatibility with HP Ada 83
31223 @section Compatibility with HP Ada 83
31226 The VMS version of GNAT fully implements all the pragmas and attributes
31227 provided by HP Ada 83, as well as providing the standard HP Ada 83
31228 libraries, including Starlet. In addition, data layouts and parameter
31229 passing conventions are highly compatible. This means that porting
31230 existing HP Ada 83 code to GNAT in VMS systems should be easier than
31231 most other porting efforts. The following are some of the most
31232 significant differences between GNAT and HP Ada 83.
31235 @item Default floating-point representation
31236 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
31237 it is VMS format. GNAT does implement the necessary pragmas
31238 (Long_Float, Float_Representation) for changing this default.
31241 The package System in GNAT exactly corresponds to the definition in the
31242 Ada 95 reference manual, which means that it excludes many of the
31243 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
31244 that contains the additional definitions, and a special pragma,
31245 Extend_System allows this package to be treated transparently as an
31246 extension of package System.
31249 The definitions provided by Aux_DEC are exactly compatible with those
31250 in the HP Ada 83 version of System, with one exception.
31251 HP Ada provides the following declarations:
31253 @smallexample @c ada
31254 TO_ADDRESS (INTEGER)
31255 TO_ADDRESS (UNSIGNED_LONGWORD)
31256 TO_ADDRESS (@i{universal_integer})
31260 The version of TO_ADDRESS taking a @i{universal integer} argument is in fact
31261 an extension to Ada 83 not strictly compatible with the reference manual.
31262 In GNAT, we are constrained to be exactly compatible with the standard,
31263 and this means we cannot provide this capability. In HP Ada 83, the
31264 point of this definition is to deal with a call like:
31266 @smallexample @c ada
31267 TO_ADDRESS (16#12777#);
31271 Normally, according to the Ada 83 standard, one would expect this to be
31272 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
31273 of TO_ADDRESS@. However, in HP Ada 83, there is no ambiguity, since the
31274 definition using @i{universal_integer} takes precedence.
31276 In GNAT, since the version with @i{universal_integer} cannot be supplied, it
31277 is not possible to be 100% compatible. Since there are many programs using
31278 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
31279 to change the name of the function in the UNSIGNED_LONGWORD case, so the
31280 declarations provided in the GNAT version of AUX_Dec are:
31282 @smallexample @c ada
31283 function To_Address (X : Integer) return Address;
31284 pragma Pure_Function (To_Address);
31286 function To_Address_Long (X : Unsigned_Longword)
31288 pragma Pure_Function (To_Address_Long);
31292 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
31293 change the name to TO_ADDRESS_LONG@.
31295 @item Task_Id values
31296 The Task_Id values assigned will be different in the two systems, and GNAT
31297 does not provide a specified value for the Task_Id of the environment task,
31298 which in GNAT is treated like any other declared task.
31302 For full details on these and other less significant compatibility issues,
31303 see appendix E of the HP publication entitled @cite{HP Ada, Technical
31304 Overview and Comparison on HP Platforms}.
31306 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
31307 attributes are recognized, although only a subset of them can sensibly
31308 be implemented. The description of pragmas in @ref{Implementation
31309 Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
31310 indicates whether or not they are applicable to non-VMS systems.
31314 @node Transitioning to 64-Bit GNAT for OpenVMS
31315 @section Transitioning to 64-Bit @value{EDITION} for OpenVMS
31318 This section is meant to assist users of pre-2006 @value{EDITION}
31319 for Alpha OpenVMS who are transitioning to 64-bit @value{EDITION},
31320 the version of the GNAT technology supplied in 2006 and later for
31321 OpenVMS on both Alpha and I64.
31324 * Introduction to transitioning::
31325 * Migration of 32 bit code::
31326 * Taking advantage of 64 bit addressing::
31327 * Technical details::
31330 @node Introduction to transitioning
31331 @subsection Introduction
31334 64-bit @value{EDITION} for Open VMS has been designed to meet
31339 Providing a full conforming implementation of Ada 95 and Ada 2005
31342 Allowing maximum backward compatibility, thus easing migration of existing
31346 Supplying a path for exploiting the full 64-bit address range
31350 Ada's strong typing semantics has made it
31351 impractical to have different 32-bit and 64-bit modes. As soon as
31352 one object could possibly be outside the 32-bit address space, this
31353 would make it necessary for the @code{System.Address} type to be 64 bits.
31354 In particular, this would cause inconsistencies if 32-bit code is
31355 called from 64-bit code that raises an exception.
31357 This issue has been resolved by always using 64-bit addressing
31358 at the system level, but allowing for automatic conversions between
31359 32-bit and 64-bit addresses where required. Thus users who
31360 do not currently require 64-bit addressing capabilities, can
31361 recompile their code with only minimal changes (and indeed
31362 if the code is written in portable Ada, with no assumptions about
31363 the size of the @code{Address} type, then no changes at all are necessary).
31365 this approach provides a simple, gradual upgrade path to future
31366 use of larger memories than available for 32-bit systems.
31367 Also, newly written applications or libraries will by default
31368 be fully compatible with future systems exploiting 64-bit
31369 addressing capabilities.
31371 @ref{Migration of 32 bit code}, will focus on porting applications
31372 that do not require more than 2 GB of
31373 addressable memory. This code will be referred to as
31374 @emph{32-bit code}.
31375 For applications intending to exploit the full 64-bit address space,
31376 @ref{Taking advantage of 64 bit addressing},
31377 will consider further changes that may be required.
31378 Such code will be referred to below as @emph{64-bit code}.
31380 @node Migration of 32 bit code
31381 @subsection Migration of 32-bit code
31386 * Unchecked conversions::
31387 * Predefined constants::
31388 * Interfacing with C::
31389 * Experience with source compatibility::
31392 @node Address types
31393 @subsubsection Address types
31396 To solve the problem of mixing 64-bit and 32-bit addressing,
31397 while maintaining maximum backward compatibility, the following
31398 approach has been taken:
31402 @code{System.Address} always has a size of 64 bits
31405 @code{System.Short_Address} is a 32-bit subtype of @code{System.Address}
31409 Since @code{System.Short_Address} is a subtype of @code{System.Address},
31410 a @code{Short_Address}
31411 may be used where an @code{Address} is required, and vice versa, without
31412 needing explicit type conversions.
31413 By virtue of the Open VMS parameter passing conventions,
31415 and exported subprograms that have 32-bit address parameters are
31416 compatible with those that have 64-bit address parameters.
31417 (See @ref{Making code 64 bit clean} for details.)
31419 The areas that may need attention are those where record types have
31420 been defined that contain components of the type @code{System.Address}, and
31421 where objects of this type are passed to code expecting a record layout with
31424 Different compilers on different platforms cannot be
31425 expected to represent the same type in the same way,
31426 since alignment constraints
31427 and other system-dependent properties affect the compiler's decision.
31428 For that reason, Ada code
31429 generally uses representation clauses to specify the expected
31430 layout where required.
31432 If such a representation clause uses 32 bits for a component having
31433 the type @code{System.Address}, 64-bit @value{EDITION} for OpenVMS
31434 will detect that error and produce a specific diagnostic message.
31435 The developer should then determine whether the representation
31436 should be 64 bits or not and make either of two changes:
31437 change the size to 64 bits and leave the type as @code{System.Address}, or
31438 leave the size as 32 bits and change the type to @code{System.Short_Address}.
31439 Since @code{Short_Address} is a subtype of @code{Address}, no changes are
31440 required in any code setting or accessing the field; the compiler will
31441 automatically perform any needed conversions between address
31445 @subsubsection Access types
31448 By default, objects designated by access values are always
31449 allocated in the 32-bit
31450 address space. Thus legacy code will never contain
31451 any objects that are not addressable with 32-bit addresses, and
31452 the compiler will never raise exceptions as result of mixing
31453 32-bit and 64-bit addresses.
31455 However, the access values themselves are represented in 64 bits, for optimum
31456 performance and future compatibility with 64-bit code. As was
31457 the case with @code{System.Address}, the compiler will give an error message
31458 if an object or record component has a representation clause that
31459 requires the access value to fit in 32 bits. In such a situation,
31460 an explicit size clause for the access type, specifying 32 bits,
31461 will have the desired effect.
31463 General access types (declared with @code{access all}) can never be
31464 32 bits, as values of such types must be able to refer to any object
31465 of the designated type,
31466 including objects residing outside the 32-bit address range.
31467 Existing Ada 83 code will not contain such type definitions,
31468 however, since general access types were introduced in Ada 95.
31470 @node Unchecked conversions
31471 @subsubsection Unchecked conversions
31474 In the case of an @code{Unchecked_Conversion} where the source type is a
31475 64-bit access type or the type @code{System.Address}, and the target
31476 type is a 32-bit type, the compiler will generate a warning.
31477 Even though the generated code will still perform the required
31478 conversions, it is highly recommended in these cases to use
31479 respectively a 32-bit access type or @code{System.Short_Address}
31480 as the source type.
31482 @node Predefined constants
31483 @subsubsection Predefined constants
31486 The following table shows the correspondence between pre-2006 versions of
31487 @value{EDITION} on Alpha OpenVMS (``Old'') and 64-bit @value{EDITION}
31490 @multitable {@code{System.Short_Memory_Size}} {2**32} {2**64}
31491 @item @b{Constant} @tab @b{Old} @tab @b{New}
31492 @item @code{System.Word_Size} @tab 32 @tab 64
31493 @item @code{System.Memory_Size} @tab 2**32 @tab 2**64
31494 @item @code{System.Short_Memory_Size} @tab 2**32 @tab 2**32
31495 @item @code{System.Address_Size} @tab 32 @tab 64
31499 If you need to refer to the specific
31500 memory size of a 32-bit implementation, instead of the
31501 actual memory size, use @code{System.Short_Memory_Size}
31502 rather than @code{System.Memory_Size}.
31503 Similarly, references to @code{System.Address_Size} may need
31504 to be replaced by @code{System.Short_Address'Size}.
31505 The program @command{gnatfind} may be useful for locating
31506 references to the above constants, so that you can verify that they
31509 @node Interfacing with C
31510 @subsubsection Interfacing with C
31513 In order to minimize the impact of the transition to 64-bit addresses on
31514 legacy programs, some fundamental types in the @code{Interfaces.C}
31515 package hierarchy continue to be represented in 32 bits.
31516 These types are: @code{ptrdiff_t}, @code{size_t}, and @code{chars_ptr}.
31517 This eases integration with the default HP C layout choices, for example
31518 as found in the system routines in @code{DECC$SHR.EXE}.
31519 Because of this implementation choice, the type fully compatible with
31520 @code{chars_ptr} is now @code{Short_Address} and not @code{Address}.
31521 Depending on the context the compiler will issue a
31522 warning or an error when type @code{Address} is used, alerting the user to a
31523 potential problem. Otherwise 32-bit programs that use
31524 @code{Interfaces.C} should normally not require code modifications
31526 The other issue arising with C interfacing concerns pragma @code{Convention}.
31527 For VMS 64-bit systems, there is an issue of the appropriate default size
31528 of C convention pointers in the absence of an explicit size clause. The HP
31529 C compiler can choose either 32 or 64 bits depending on compiler options.
31530 GNAT chooses 32-bits rather than 64-bits in the default case where no size
31531 clause is given. This proves a better choice for porting 32-bit legacy
31532 applications. In order to have a 64-bit representation, it is necessary to
31533 specify a size representation clause. For example:
31535 @smallexample @c ada
31536 type int_star is access Interfaces.C.int;
31537 pragma Convention(C, int_star);
31538 for int_star'Size use 64; -- Necessary to get 64 and not 32 bits
31541 @node Experience with source compatibility
31542 @subsubsection Experience with source compatibility
31545 The Security Server and STARLET on I64 provide an interesting ``test case''
31546 for source compatibility issues, since it is in such system code
31547 where assumptions about @code{Address} size might be expected to occur.
31548 Indeed, there were a small number of occasions in the Security Server
31549 file @file{jibdef.ads}
31550 where a representation clause for a record type specified
31551 32 bits for a component of type @code{Address}.
31552 All of these errors were detected by the compiler.
31553 The repair was obvious and immediate; to simply replace @code{Address} by
31554 @code{Short_Address}.
31556 In the case of STARLET, there were several record types that should
31557 have had representation clauses but did not. In these record types
31558 there was an implicit assumption that an @code{Address} value occupied
31560 These compiled without error, but their usage resulted in run-time error
31561 returns from STARLET system calls.
31562 Future GNAT technology enhancements may include a tool that detects and flags
31563 these sorts of potential source code porting problems.
31565 @c ****************************************
31566 @node Taking advantage of 64 bit addressing
31567 @subsection Taking advantage of 64-bit addressing
31570 * Making code 64 bit clean::
31571 * Allocating memory from the 64 bit storage pool::
31572 * Restrictions on use of 64 bit objects::
31573 * Using 64 bit storage pools by default::
31574 * General access types::
31575 * STARLET and other predefined libraries::
31578 @node Making code 64 bit clean
31579 @subsubsection Making code 64-bit clean
31582 In order to prevent problems that may occur when (parts of) a
31583 system start using memory outside the 32-bit address range,
31584 we recommend some additional guidelines:
31588 For imported subprograms that take parameters of the
31589 type @code{System.Address}, ensure that these subprograms can
31590 indeed handle 64-bit addresses. If not, or when in doubt,
31591 change the subprogram declaration to specify
31592 @code{System.Short_Address} instead.
31595 Resolve all warnings related to size mismatches in
31596 unchecked conversions. Failing to do so causes
31597 erroneous execution if the source object is outside
31598 the 32-bit address space.
31601 (optional) Explicitly use the 32-bit storage pool
31602 for access types used in a 32-bit context, or use
31603 generic access types where possible
31604 (@pxref{Restrictions on use of 64 bit objects}).
31608 If these rules are followed, the compiler will automatically insert
31609 any necessary checks to ensure that no addresses or access values
31610 passed to 32-bit code ever refer to objects outside the 32-bit
31612 Any attempt to do this will raise @code{Constraint_Error}.
31614 @node Allocating memory from the 64 bit storage pool
31615 @subsubsection Allocating memory from the 64-bit storage pool
31618 For any access type @code{T} that potentially requires memory allocations
31619 beyond the 32-bit address space,
31620 use the following representation clause:
31622 @smallexample @c ada
31623 for T'Storage_Pool use System.Pool_64;
31626 @node Restrictions on use of 64 bit objects
31627 @subsubsection Restrictions on use of 64-bit objects
31630 Taking the address of an object allocated from a 64-bit storage pool,
31631 and then passing this address to a subprogram expecting
31632 @code{System.Short_Address},
31633 or assigning it to a variable of type @code{Short_Address}, will cause
31634 @code{Constraint_Error} to be raised. In case the code is not 64-bit clean
31635 (@pxref{Making code 64 bit clean}), or checks are suppressed,
31636 no exception is raised and execution
31637 will become erroneous.
31639 @node Using 64 bit storage pools by default
31640 @subsubsection Using 64-bit storage pools by default
31643 In some cases it may be desirable to have the compiler allocate
31644 from 64-bit storage pools by default. This may be the case for
31645 libraries that are 64-bit clean, but may be used in both 32-bit
31646 and 64-bit contexts. For these cases the following configuration
31647 pragma may be specified:
31649 @smallexample @c ada
31650 pragma Pool_64_Default;
31654 Any code compiled in the context of this pragma will by default
31655 use the @code{System.Pool_64} storage pool. This default may be overridden
31656 for a specific access type @code{T} by the representation clause:
31658 @smallexample @c ada
31659 for T'Storage_Pool use System.Pool_32;
31663 Any object whose address may be passed to a subprogram with a
31664 @code{Short_Address} argument, or assigned to a variable of type
31665 @code{Short_Address}, needs to be allocated from this pool.
31667 @node General access types
31668 @subsubsection General access types
31671 Objects designated by access values from a
31672 general access type (declared with @code{access all}) are never allocated
31673 from a 64-bit storage pool. Code that uses general access types will
31674 accept objects allocated in either 32-bit or 64-bit address spaces,
31675 but never allocate objects outside the 32-bit address space.
31676 Using general access types ensures maximum compatibility with both
31677 32-bit and 64-bit code.
31679 @node STARLET and other predefined libraries
31680 @subsubsection STARLET and other predefined libraries
31683 All code that comes as part of GNAT is 64-bit clean, but the
31684 restrictions given in @ref{Restrictions on use of 64 bit objects},
31685 still apply. Look at the package
31686 specs to see in which contexts objects allocated
31687 in 64-bit address space are acceptable.
31689 @node Technical details
31690 @subsection Technical details
31693 64-bit @value{EDITION} for Open VMS takes advantage of the freedom given in the
31694 Ada standard with respect to the type of @code{System.Address}. Previous
31695 versions of GNAT Pro have defined this type as private and implemented it as a
31698 In order to allow defining @code{System.Short_Address} as a proper subtype,
31699 and to match the implicit sign extension in parameter passing,
31700 in 64-bit @value{EDITION} for Open VMS, @code{System.Address} is defined as a
31701 visible (i.e., non-private) integer type.
31702 Standard operations on the type, such as the binary operators ``+'', ``-'',
31703 etc., that take @code{Address} operands and return an @code{Address} result,
31704 have been hidden by declaring these
31705 @code{abstract}, a feature introduced in Ada 95 that helps avoid the potential
31706 ambiguities that would otherwise result from overloading.
31707 (Note that, although @code{Address} is a visible integer type,
31708 good programming practice dictates against exploiting the type's
31709 integer properties such as literals, since this will compromise
31712 Defining @code{Address} as a visible integer type helps achieve
31713 maximum compatibility for existing Ada code,
31714 without sacrificing the capabilities of the 64-bit architecture.
31717 @c ************************************************
31719 @node Microsoft Windows Topics
31720 @appendix Microsoft Windows Topics
31726 This chapter describes topics that are specific to the Microsoft Windows
31727 platforms (NT, 2000, and XP Professional).
31730 * Using GNAT on Windows::
31731 * Using a network installation of GNAT::
31732 * CONSOLE and WINDOWS subsystems::
31733 * Temporary Files::
31734 * Mixed-Language Programming on Windows::
31735 * Windows Calling Conventions::
31736 * Introduction to Dynamic Link Libraries (DLLs)::
31737 * Using DLLs with GNAT::
31738 * Building DLLs with GNAT::
31739 * Building DLLs with GNAT Project files::
31740 * Building DLLs with gnatdll::
31741 * GNAT and Windows Resources::
31742 * Debugging a DLL::
31743 * Setting Stack Size from gnatlink::
31744 * Setting Heap Size from gnatlink::
31747 @node Using GNAT on Windows
31748 @section Using GNAT on Windows
31751 One of the strengths of the GNAT technology is that its tool set
31752 (@command{gcc}, @command{gnatbind}, @command{gnatlink}, @command{gnatmake}, the
31753 @code{gdb} debugger, etc.) is used in the same way regardless of the
31756 On Windows this tool set is complemented by a number of Microsoft-specific
31757 tools that have been provided to facilitate interoperability with Windows
31758 when this is required. With these tools:
31763 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
31767 You can use any Dynamically Linked Library (DLL) in your Ada code (both
31768 relocatable and non-relocatable DLLs are supported).
31771 You can build Ada DLLs for use in other applications. These applications
31772 can be written in a language other than Ada (e.g., C, C++, etc). Again both
31773 relocatable and non-relocatable Ada DLLs are supported.
31776 You can include Windows resources in your Ada application.
31779 You can use or create COM/DCOM objects.
31783 Immediately below are listed all known general GNAT-for-Windows restrictions.
31784 Other restrictions about specific features like Windows Resources and DLLs
31785 are listed in separate sections below.
31790 It is not possible to use @code{GetLastError} and @code{SetLastError}
31791 when tasking, protected records, or exceptions are used. In these
31792 cases, in order to implement Ada semantics, the GNAT run-time system
31793 calls certain Win32 routines that set the last error variable to 0 upon
31794 success. It should be possible to use @code{GetLastError} and
31795 @code{SetLastError} when tasking, protected record, and exception
31796 features are not used, but it is not guaranteed to work.
31799 It is not possible to link against Microsoft libraries except for
31800 import libraries. The library must be built to be compatible with
31801 @file{MSVCRT.LIB} (/MD Microsoft compiler option), @file{LIBC.LIB} and
31802 @file{LIBCMT.LIB} (/ML or /MT Microsoft compiler options) are known to
31803 not be compatible with the GNAT runtime. Even if the library is
31804 compatible with @file{MSVCRT.LIB} it is not guaranteed to work.
31807 When the compilation environment is located on FAT32 drives, users may
31808 experience recompilations of the source files that have not changed if
31809 Daylight Saving Time (DST) state has changed since the last time files
31810 were compiled. NTFS drives do not have this problem.
31813 No components of the GNAT toolset use any entries in the Windows
31814 registry. The only entries that can be created are file associations and
31815 PATH settings, provided the user has chosen to create them at installation
31816 time, as well as some minimal book-keeping information needed to correctly
31817 uninstall or integrate different GNAT products.
31820 @node Using a network installation of GNAT
31821 @section Using a network installation of GNAT
31824 Make sure the system on which GNAT is installed is accessible from the
31825 current machine, i.e., the install location is shared over the network.
31826 Shared resources are accessed on Windows by means of UNC paths, which
31827 have the format @code{\\server\sharename\path}
31829 In order to use such a network installation, simply add the UNC path of the
31830 @file{bin} directory of your GNAT installation in front of your PATH. For
31831 example, if GNAT is installed in @file{\GNAT} directory of a share location
31832 called @file{c-drive} on a machine @file{LOKI}, the following command will
31835 @code{@ @ @ path \\loki\c-drive\gnat\bin;%path%}
31837 Be aware that every compilation using the network installation results in the
31838 transfer of large amounts of data across the network and will likely cause
31839 serious performance penalty.
31841 @node CONSOLE and WINDOWS subsystems
31842 @section CONSOLE and WINDOWS subsystems
31843 @cindex CONSOLE Subsystem
31844 @cindex WINDOWS Subsystem
31848 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
31849 (which is the default subsystem) will always create a console when
31850 launching the application. This is not something desirable when the
31851 application has a Windows GUI. To get rid of this console the
31852 application must be using the @code{WINDOWS} subsystem. To do so
31853 the @option{-mwindows} linker option must be specified.
31856 $ gnatmake winprog -largs -mwindows
31859 @node Temporary Files
31860 @section Temporary Files
31861 @cindex Temporary files
31864 It is possible to control where temporary files gets created by setting
31865 the @env{TMP} environment variable. The file will be created:
31868 @item Under the directory pointed to by the @env{TMP} environment variable if
31869 this directory exists.
31871 @item Under @file{c:\temp}, if the @env{TMP} environment variable is not
31872 set (or not pointing to a directory) and if this directory exists.
31874 @item Under the current working directory otherwise.
31878 This allows you to determine exactly where the temporary
31879 file will be created. This is particularly useful in networked
31880 environments where you may not have write access to some
31883 @node Mixed-Language Programming on Windows
31884 @section Mixed-Language Programming on Windows
31887 Developing pure Ada applications on Windows is no different than on
31888 other GNAT-supported platforms. However, when developing or porting an
31889 application that contains a mix of Ada and C/C++, the choice of your
31890 Windows C/C++ development environment conditions your overall
31891 interoperability strategy.
31893 If you use @command{gcc} to compile the non-Ada part of your application,
31894 there are no Windows-specific restrictions that affect the overall
31895 interoperability with your Ada code. If you plan to use
31896 Microsoft tools (e.g.@: Microsoft Visual C/C++), you should be aware of
31897 the following limitations:
31901 You cannot link your Ada code with an object or library generated with
31902 Microsoft tools if these use the @code{.tls} section (Thread Local
31903 Storage section) since the GNAT linker does not yet support this section.
31906 You cannot link your Ada code with an object or library generated with
31907 Microsoft tools if these use I/O routines other than those provided in
31908 the Microsoft DLL: @code{msvcrt.dll}. This is because the GNAT run time
31909 uses the services of @code{msvcrt.dll} for its I/Os. Use of other I/O
31910 libraries can cause a conflict with @code{msvcrt.dll} services. For
31911 instance Visual C++ I/O stream routines conflict with those in
31916 If you do want to use the Microsoft tools for your non-Ada code and hit one
31917 of the above limitations, you have two choices:
31921 Encapsulate your non-Ada code in a DLL to be linked with your Ada
31922 application. In this case, use the Microsoft or whatever environment to
31923 build the DLL and use GNAT to build your executable
31924 (@pxref{Using DLLs with GNAT}).
31927 Or you can encapsulate your Ada code in a DLL to be linked with the
31928 other part of your application. In this case, use GNAT to build the DLL
31929 (@pxref{Building DLLs with GNAT}) and use the Microsoft or whatever
31930 environment to build your executable.
31933 @node Windows Calling Conventions
31934 @section Windows Calling Conventions
31939 * C Calling Convention::
31940 * Stdcall Calling Convention::
31941 * Win32 Calling Convention::
31942 * DLL Calling Convention::
31946 When a subprogram @code{F} (caller) calls a subprogram @code{G}
31947 (callee), there are several ways to push @code{G}'s parameters on the
31948 stack and there are several possible scenarios to clean up the stack
31949 upon @code{G}'s return. A calling convention is an agreed upon software
31950 protocol whereby the responsibilities between the caller (@code{F}) and
31951 the callee (@code{G}) are clearly defined. Several calling conventions
31952 are available for Windows:
31956 @code{C} (Microsoft defined)
31959 @code{Stdcall} (Microsoft defined)
31962 @code{Win32} (GNAT specific)
31965 @code{DLL} (GNAT specific)
31968 @node C Calling Convention
31969 @subsection @code{C} Calling Convention
31972 This is the default calling convention used when interfacing to C/C++
31973 routines compiled with either @command{gcc} or Microsoft Visual C++.
31975 In the @code{C} calling convention subprogram parameters are pushed on the
31976 stack by the caller from right to left. The caller itself is in charge of
31977 cleaning up the stack after the call. In addition, the name of a routine
31978 with @code{C} calling convention is mangled by adding a leading underscore.
31980 The name to use on the Ada side when importing (or exporting) a routine
31981 with @code{C} calling convention is the name of the routine. For
31982 instance the C function:
31985 int get_val (long);
31989 should be imported from Ada as follows:
31991 @smallexample @c ada
31993 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31994 pragma Import (C, Get_Val, External_Name => "get_val");
31999 Note that in this particular case the @code{External_Name} parameter could
32000 have been omitted since, when missing, this parameter is taken to be the
32001 name of the Ada entity in lower case. When the @code{Link_Name} parameter
32002 is missing, as in the above example, this parameter is set to be the
32003 @code{External_Name} with a leading underscore.
32005 When importing a variable defined in C, you should always use the @code{C}
32006 calling convention unless the object containing the variable is part of a
32007 DLL (in which case you should use the @code{Stdcall} calling
32008 convention, @pxref{Stdcall Calling Convention}).
32010 @node Stdcall Calling Convention
32011 @subsection @code{Stdcall} Calling Convention
32014 This convention, which was the calling convention used for Pascal
32015 programs, is used by Microsoft for all the routines in the Win32 API for
32016 efficiency reasons. It must be used to import any routine for which this
32017 convention was specified.
32019 In the @code{Stdcall} calling convention subprogram parameters are pushed
32020 on the stack by the caller from right to left. The callee (and not the
32021 caller) is in charge of cleaning the stack on routine exit. In addition,
32022 the name of a routine with @code{Stdcall} calling convention is mangled by
32023 adding a leading underscore (as for the @code{C} calling convention) and a
32024 trailing @code{@@}@code{@var{nn}}, where @var{nn} is the overall size (in
32025 bytes) of the parameters passed to the routine.
32027 The name to use on the Ada side when importing a C routine with a
32028 @code{Stdcall} calling convention is the name of the C routine. The leading
32029 underscore and trailing @code{@@}@code{@var{nn}} are added automatically by
32030 the compiler. For instance the Win32 function:
32033 @b{APIENTRY} int get_val (long);
32037 should be imported from Ada as follows:
32039 @smallexample @c ada
32041 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
32042 pragma Import (Stdcall, Get_Val);
32043 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
32048 As for the @code{C} calling convention, when the @code{External_Name}
32049 parameter is missing, it is taken to be the name of the Ada entity in lower
32050 case. If instead of writing the above import pragma you write:
32052 @smallexample @c ada
32054 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
32055 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
32060 then the imported routine is @code{_retrieve_val@@4}. However, if instead
32061 of specifying the @code{External_Name} parameter you specify the
32062 @code{Link_Name} as in the following example:
32064 @smallexample @c ada
32066 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
32067 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
32072 then the imported routine is @code{retrieve_val}, that is, there is no
32073 decoration at all. No leading underscore and no Stdcall suffix
32074 @code{@@}@code{@var{nn}}.
32077 This is especially important as in some special cases a DLL's entry
32078 point name lacks a trailing @code{@@}@code{@var{nn}} while the exported
32079 name generated for a call has it.
32082 It is also possible to import variables defined in a DLL by using an
32083 import pragma for a variable. As an example, if a DLL contains a
32084 variable defined as:
32091 then, to access this variable from Ada you should write:
32093 @smallexample @c ada
32095 My_Var : Interfaces.C.int;
32096 pragma Import (Stdcall, My_Var);
32101 Note that to ease building cross-platform bindings this convention
32102 will be handled as a @code{C} calling convention on non-Windows platforms.
32104 @node Win32 Calling Convention
32105 @subsection @code{Win32} Calling Convention
32108 This convention, which is GNAT-specific is fully equivalent to the
32109 @code{Stdcall} calling convention described above.
32111 @node DLL Calling Convention
32112 @subsection @code{DLL} Calling Convention
32115 This convention, which is GNAT-specific is fully equivalent to the
32116 @code{Stdcall} calling convention described above.
32118 @node Introduction to Dynamic Link Libraries (DLLs)
32119 @section Introduction to Dynamic Link Libraries (DLLs)
32123 A Dynamically Linked Library (DLL) is a library that can be shared by
32124 several applications running under Windows. A DLL can contain any number of
32125 routines and variables.
32127 One advantage of DLLs is that you can change and enhance them without
32128 forcing all the applications that depend on them to be relinked or
32129 recompiled. However, you should be aware than all calls to DLL routines are
32130 slower since, as you will understand below, such calls are indirect.
32132 To illustrate the remainder of this section, suppose that an application
32133 wants to use the services of a DLL @file{API.dll}. To use the services
32134 provided by @file{API.dll} you must statically link against the DLL or
32135 an import library which contains a jump table with an entry for each
32136 routine and variable exported by the DLL. In the Microsoft world this
32137 import library is called @file{API.lib}. When using GNAT this import
32138 library is called either @file{libAPI.dll.a}, @file{libapi.dll.a},
32139 @file{libAPI.a} or @file{libapi.a} (names are case insensitive).
32141 After you have linked your application with the DLL or the import library
32142 and you run your application, here is what happens:
32146 Your application is loaded into memory.
32149 The DLL @file{API.dll} is mapped into the address space of your
32150 application. This means that:
32154 The DLL will use the stack of the calling thread.
32157 The DLL will use the virtual address space of the calling process.
32160 The DLL will allocate memory from the virtual address space of the calling
32164 Handles (pointers) can be safely exchanged between routines in the DLL
32165 routines and routines in the application using the DLL.
32169 The entries in the jump table (from the import library @file{libAPI.dll.a}
32170 or @file{API.lib} or automatically created when linking against a DLL)
32171 which is part of your application are initialized with the addresses
32172 of the routines and variables in @file{API.dll}.
32175 If present in @file{API.dll}, routines @code{DllMain} or
32176 @code{DllMainCRTStartup} are invoked. These routines typically contain
32177 the initialization code needed for the well-being of the routines and
32178 variables exported by the DLL.
32182 There is an additional point which is worth mentioning. In the Windows
32183 world there are two kind of DLLs: relocatable and non-relocatable
32184 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
32185 in the target application address space. If the addresses of two
32186 non-relocatable DLLs overlap and these happen to be used by the same
32187 application, a conflict will occur and the application will run
32188 incorrectly. Hence, when possible, it is always preferable to use and
32189 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
32190 supported by GNAT. Note that the @option{-s} linker option (see GNU Linker
32191 User's Guide) removes the debugging symbols from the DLL but the DLL can
32192 still be relocated.
32194 As a side note, an interesting difference between Microsoft DLLs and
32195 Unix shared libraries, is the fact that on most Unix systems all public
32196 routines are exported by default in a Unix shared library, while under
32197 Windows it is possible (but not required) to list exported routines in
32198 a definition file (@pxref{The Definition File}).
32200 @node Using DLLs with GNAT
32201 @section Using DLLs with GNAT
32204 * Creating an Ada Spec for the DLL Services::
32205 * Creating an Import Library::
32209 To use the services of a DLL, say @file{API.dll}, in your Ada application
32214 The Ada spec for the routines and/or variables you want to access in
32215 @file{API.dll}. If not available this Ada spec must be built from the C/C++
32216 header files provided with the DLL.
32219 The import library (@file{libAPI.dll.a} or @file{API.lib}). As previously
32220 mentioned an import library is a statically linked library containing the
32221 import table which will be filled at load time to point to the actual
32222 @file{API.dll} routines. Sometimes you don't have an import library for the
32223 DLL you want to use. The following sections will explain how to build
32224 one. Note that this is optional.
32227 The actual DLL, @file{API.dll}.
32231 Once you have all the above, to compile an Ada application that uses the
32232 services of @file{API.dll} and whose main subprogram is @code{My_Ada_App},
32233 you simply issue the command
32236 $ gnatmake my_ada_app -largs -lAPI
32240 The argument @option{-largs -lAPI} at the end of the @command{gnatmake} command
32241 tells the GNAT linker to look first for a library named @file{API.lib}
32242 (Microsoft-style name) and if not found for a libraries named
32243 @file{libAPI.dll.a}, @file{API.dll.a} or @file{libAPI.a}.
32244 (GNAT-style name). Note that if the Ada package spec for @file{API.dll}
32245 contains the following pragma
32247 @smallexample @c ada
32248 pragma Linker_Options ("-lAPI");
32252 you do not have to add @option{-largs -lAPI} at the end of the
32253 @command{gnatmake} command.
32255 If any one of the items above is missing you will have to create it
32256 yourself. The following sections explain how to do so using as an
32257 example a fictitious DLL called @file{API.dll}.
32259 @node Creating an Ada Spec for the DLL Services
32260 @subsection Creating an Ada Spec for the DLL Services
32263 A DLL typically comes with a C/C++ header file which provides the
32264 definitions of the routines and variables exported by the DLL. The Ada
32265 equivalent of this header file is a package spec that contains definitions
32266 for the imported entities. If the DLL you intend to use does not come with
32267 an Ada spec you have to generate one such spec yourself. For example if
32268 the header file of @file{API.dll} is a file @file{api.h} containing the
32269 following two definitions:
32281 then the equivalent Ada spec could be:
32283 @smallexample @c ada
32286 with Interfaces.C.Strings;
32291 function Get (Str : C.Strings.Chars_Ptr) return C.int;
32294 pragma Import (C, Get);
32295 pragma Import (DLL, Some_Var);
32302 Note that a variable is
32303 @strong{always imported with a Stdcall convention}. A function
32304 can have @code{C} or @code{Stdcall} convention.
32305 (@pxref{Windows Calling Conventions}).
32307 @node Creating an Import Library
32308 @subsection Creating an Import Library
32309 @cindex Import library
32312 * The Definition File::
32313 * GNAT-Style Import Library::
32314 * Microsoft-Style Import Library::
32318 If a Microsoft-style import library @file{API.lib} or a GNAT-style
32319 import library @file{libAPI.dll.a} or @file{libAPI.a} is available
32320 with @file{API.dll} you can skip this section. You can also skip this
32321 section if @file{API.dll} or @file{libAPI.dll} is built with GNU tools
32322 as in this case it is possible to link directly against the
32323 DLL. Otherwise read on.
32325 @node The Definition File
32326 @subsubsection The Definition File
32327 @cindex Definition file
32331 As previously mentioned, and unlike Unix systems, the list of symbols
32332 that are exported from a DLL must be provided explicitly in Windows.
32333 The main goal of a definition file is precisely that: list the symbols
32334 exported by a DLL. A definition file (usually a file with a @code{.def}
32335 suffix) has the following structure:
32340 @r{[}LIBRARY @var{name}@r{]}
32341 @r{[}DESCRIPTION @var{string}@r{]}
32351 @item LIBRARY @var{name}
32352 This section, which is optional, gives the name of the DLL.
32354 @item DESCRIPTION @var{string}
32355 This section, which is optional, gives a description string that will be
32356 embedded in the import library.
32359 This section gives the list of exported symbols (procedures, functions or
32360 variables). For instance in the case of @file{API.dll} the @code{EXPORTS}
32361 section of @file{API.def} looks like:
32375 Note that you must specify the correct suffix (@code{@@}@code{@var{nn}})
32376 (@pxref{Windows Calling Conventions}) for a Stdcall
32377 calling convention function in the exported symbols list.
32380 There can actually be other sections in a definition file, but these
32381 sections are not relevant to the discussion at hand.
32383 @node GNAT-Style Import Library
32384 @subsubsection GNAT-Style Import Library
32387 To create a static import library from @file{API.dll} with the GNAT tools
32388 you should proceed as follows:
32392 Create the definition file @file{API.def} (@pxref{The Definition File}).
32393 For that use the @code{dll2def} tool as follows:
32396 $ dll2def API.dll > API.def
32400 @code{dll2def} is a very simple tool: it takes as input a DLL and prints
32401 to standard output the list of entry points in the DLL. Note that if
32402 some routines in the DLL have the @code{Stdcall} convention
32403 (@pxref{Windows Calling Conventions}) with stripped @code{@@}@var{nn}
32404 suffix then you'll have to edit @file{api.def} to add it, and specify
32405 @option{-k} to @command{gnatdll} when creating the import library.
32408 Here are some hints to find the right @code{@@}@var{nn} suffix.
32412 If you have the Microsoft import library (.lib), it is possible to get
32413 the right symbols by using Microsoft @code{dumpbin} tool (see the
32414 corresponding Microsoft documentation for further details).
32417 $ dumpbin /exports api.lib
32421 If you have a message about a missing symbol at link time the compiler
32422 tells you what symbol is expected. You just have to go back to the
32423 definition file and add the right suffix.
32427 Build the import library @code{libAPI.dll.a}, using @code{gnatdll}
32428 (@pxref{Using gnatdll}) as follows:
32431 $ gnatdll -e API.def -d API.dll
32435 @code{gnatdll} takes as input a definition file @file{API.def} and the
32436 name of the DLL containing the services listed in the definition file
32437 @file{API.dll}. The name of the static import library generated is
32438 computed from the name of the definition file as follows: if the
32439 definition file name is @var{xyz}@code{.def}, the import library name will
32440 be @code{lib}@var{xyz}@code{.a}. Note that in the previous example option
32441 @option{-e} could have been removed because the name of the definition
32442 file (before the ``@code{.def}'' suffix) is the same as the name of the
32443 DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}).
32446 @node Microsoft-Style Import Library
32447 @subsubsection Microsoft-Style Import Library
32450 With GNAT you can either use a GNAT-style or Microsoft-style import
32451 library. A Microsoft import library is needed only if you plan to make an
32452 Ada DLL available to applications developed with Microsoft
32453 tools (@pxref{Mixed-Language Programming on Windows}).
32455 To create a Microsoft-style import library for @file{API.dll} you
32456 should proceed as follows:
32460 Create the definition file @file{API.def} from the DLL. For this use either
32461 the @code{dll2def} tool as described above or the Microsoft @code{dumpbin}
32462 tool (see the corresponding Microsoft documentation for further details).
32465 Build the actual import library using Microsoft's @code{lib} utility:
32468 $ lib -machine:IX86 -def:API.def -out:API.lib
32472 If you use the above command the definition file @file{API.def} must
32473 contain a line giving the name of the DLL:
32480 See the Microsoft documentation for further details about the usage of
32484 @node Building DLLs with GNAT
32485 @section Building DLLs with GNAT
32486 @cindex DLLs, building
32489 This section explain how to build DLLs using the GNAT built-in DLL
32490 support. With the following procedure it is straight forward to build
32491 and use DLLs with GNAT.
32495 @item building object files
32497 The first step is to build all objects files that are to be included
32498 into the DLL. This is done by using the standard @command{gnatmake} tool.
32500 @item building the DLL
32502 To build the DLL you must use @command{gcc}'s @option{-shared}
32503 option. It is quite simple to use this method:
32506 $ gcc -shared -o api.dll obj1.o obj2.o @dots{}
32509 It is important to note that in this case all symbols found in the
32510 object files are automatically exported. It is possible to restrict
32511 the set of symbols to export by passing to @command{gcc} a definition
32512 file, @pxref{The Definition File}. For example:
32515 $ gcc -shared -o api.dll api.def obj1.o obj2.o @dots{}
32518 If you use a definition file you must export the elaboration procedures
32519 for every package that required one. Elaboration procedures are named
32520 using the package name followed by "_E".
32522 @item preparing DLL to be used
32524 For the DLL to be used by client programs the bodies must be hidden
32525 from it and the .ali set with read-only attribute. This is very important
32526 otherwise GNAT will recompile all packages and will not actually use
32527 the code in the DLL. For example:
32531 $ copy *.ads *.ali api.dll apilib
32532 $ attrib +R apilib\*.ali
32537 At this point it is possible to use the DLL by directly linking
32538 against it. Note that you must use the GNAT shared runtime when using
32539 GNAT shared libraries. This is achieved by using @option{-shared} binder's
32543 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
32546 @node Building DLLs with GNAT Project files
32547 @section Building DLLs with GNAT Project files
32548 @cindex DLLs, building
32551 There is nothing specific to Windows in the build process.
32552 @pxref{Library Projects}.
32555 Due to a system limitation, it is not possible under Windows to create threads
32556 when inside the @code{DllMain} routine which is used for auto-initialization
32557 of shared libraries, so it is not possible to have library level tasks in SALs.
32559 @node Building DLLs with gnatdll
32560 @section Building DLLs with gnatdll
32561 @cindex DLLs, building
32564 * Limitations When Using Ada DLLs from Ada::
32565 * Exporting Ada Entities::
32566 * Ada DLLs and Elaboration::
32567 * Ada DLLs and Finalization::
32568 * Creating a Spec for Ada DLLs::
32569 * Creating the Definition File::
32574 Note that it is preferred to use the built-in GNAT DLL support
32575 (@pxref{Building DLLs with GNAT}) or GNAT Project files
32576 (@pxref{Building DLLs with GNAT Project files}) to build DLLs.
32578 This section explains how to build DLLs containing Ada code using
32579 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
32580 remainder of this section.
32582 The steps required to build an Ada DLL that is to be used by Ada as well as
32583 non-Ada applications are as follows:
32587 You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or
32588 @code{Stdcall} calling convention to avoid any Ada name mangling for the
32589 entities exported by the DLL (@pxref{Exporting Ada Entities}). You can
32590 skip this step if you plan to use the Ada DLL only from Ada applications.
32593 Your Ada code must export an initialization routine which calls the routine
32594 @code{adainit} generated by @command{gnatbind} to perform the elaboration of
32595 the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization
32596 routine exported by the Ada DLL must be invoked by the clients of the DLL
32597 to initialize the DLL.
32600 When useful, the DLL should also export a finalization routine which calls
32601 routine @code{adafinal} generated by @command{gnatbind} to perform the
32602 finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}).
32603 The finalization routine exported by the Ada DLL must be invoked by the
32604 clients of the DLL when the DLL services are no further needed.
32607 You must provide a spec for the services exported by the Ada DLL in each
32608 of the programming languages to which you plan to make the DLL available.
32611 You must provide a definition file listing the exported entities
32612 (@pxref{The Definition File}).
32615 Finally you must use @code{gnatdll} to produce the DLL and the import
32616 library (@pxref{Using gnatdll}).
32620 Note that a relocatable DLL stripped using the @code{strip}
32621 binutils tool will not be relocatable anymore. To build a DLL without
32622 debug information pass @code{-largs -s} to @code{gnatdll}. This
32623 restriction does not apply to a DLL built using a Library Project.
32624 @pxref{Library Projects}.
32626 @node Limitations When Using Ada DLLs from Ada
32627 @subsection Limitations When Using Ada DLLs from Ada
32630 When using Ada DLLs from Ada applications there is a limitation users
32631 should be aware of. Because on Windows the GNAT run time is not in a DLL of
32632 its own, each Ada DLL includes a part of the GNAT run time. Specifically,
32633 each Ada DLL includes the services of the GNAT run time that are necessary
32634 to the Ada code inside the DLL. As a result, when an Ada program uses an
32635 Ada DLL there are two independent GNAT run times: one in the Ada DLL and
32636 one in the main program.
32638 It is therefore not possible to exchange GNAT run-time objects between the
32639 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
32640 handles (e.g.@: @code{Text_IO.File_Type}), tasks types, protected objects
32643 It is completely safe to exchange plain elementary, array or record types,
32644 Windows object handles, etc.
32646 @node Exporting Ada Entities
32647 @subsection Exporting Ada Entities
32648 @cindex Export table
32651 Building a DLL is a way to encapsulate a set of services usable from any
32652 application. As a result, the Ada entities exported by a DLL should be
32653 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
32654 any Ada name mangling. As an example here is an Ada package
32655 @code{API}, spec and body, exporting two procedures, a function, and a
32658 @smallexample @c ada
32661 with Interfaces.C; use Interfaces;
32663 Count : C.int := 0;
32664 function Factorial (Val : C.int) return C.int;
32666 procedure Initialize_API;
32667 procedure Finalize_API;
32668 -- Initialization & Finalization routines. More in the next section.
32670 pragma Export (C, Initialize_API);
32671 pragma Export (C, Finalize_API);
32672 pragma Export (C, Count);
32673 pragma Export (C, Factorial);
32679 @smallexample @c ada
32682 package body API is
32683 function Factorial (Val : C.int) return C.int is
32686 Count := Count + 1;
32687 for K in 1 .. Val loop
32693 procedure Initialize_API is
32695 pragma Import (C, Adainit);
32698 end Initialize_API;
32700 procedure Finalize_API is
32701 procedure Adafinal;
32702 pragma Import (C, Adafinal);
32712 If the Ada DLL you are building will only be used by Ada applications
32713 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
32714 convention. As an example, the previous package could be written as
32717 @smallexample @c ada
32721 Count : Integer := 0;
32722 function Factorial (Val : Integer) return Integer;
32724 procedure Initialize_API;
32725 procedure Finalize_API;
32726 -- Initialization and Finalization routines.
32732 @smallexample @c ada
32735 package body API is
32736 function Factorial (Val : Integer) return Integer is
32737 Fact : Integer := 1;
32739 Count := Count + 1;
32740 for K in 1 .. Val loop
32747 -- The remainder of this package body is unchanged.
32754 Note that if you do not export the Ada entities with a @code{C} or
32755 @code{Stdcall} convention you will have to provide the mangled Ada names
32756 in the definition file of the Ada DLL
32757 (@pxref{Creating the Definition File}).
32759 @node Ada DLLs and Elaboration
32760 @subsection Ada DLLs and Elaboration
32761 @cindex DLLs and elaboration
32764 The DLL that you are building contains your Ada code as well as all the
32765 routines in the Ada library that are needed by it. The first thing a
32766 user of your DLL must do is elaborate the Ada code
32767 (@pxref{Elaboration Order Handling in GNAT}).
32769 To achieve this you must export an initialization routine
32770 (@code{Initialize_API} in the previous example), which must be invoked
32771 before using any of the DLL services. This elaboration routine must call
32772 the Ada elaboration routine @code{adainit} generated by the GNAT binder
32773 (@pxref{Binding with Non-Ada Main Programs}). See the body of
32774 @code{Initialize_Api} for an example. Note that the GNAT binder is
32775 automatically invoked during the DLL build process by the @code{gnatdll}
32776 tool (@pxref{Using gnatdll}).
32778 When a DLL is loaded, Windows systematically invokes a routine called
32779 @code{DllMain}. It would therefore be possible to call @code{adainit}
32780 directly from @code{DllMain} without having to provide an explicit
32781 initialization routine. Unfortunately, it is not possible to call
32782 @code{adainit} from the @code{DllMain} if your program has library level
32783 tasks because access to the @code{DllMain} entry point is serialized by
32784 the system (that is, only a single thread can execute ``through'' it at a
32785 time), which means that the GNAT run time will deadlock waiting for the
32786 newly created task to complete its initialization.
32788 @node Ada DLLs and Finalization
32789 @subsection Ada DLLs and Finalization
32790 @cindex DLLs and finalization
32793 When the services of an Ada DLL are no longer needed, the client code should
32794 invoke the DLL finalization routine, if available. The DLL finalization
32795 routine is in charge of releasing all resources acquired by the DLL. In the
32796 case of the Ada code contained in the DLL, this is achieved by calling
32797 routine @code{adafinal} generated by the GNAT binder
32798 (@pxref{Binding with Non-Ada Main Programs}).
32799 See the body of @code{Finalize_Api} for an
32800 example. As already pointed out the GNAT binder is automatically invoked
32801 during the DLL build process by the @code{gnatdll} tool
32802 (@pxref{Using gnatdll}).
32804 @node Creating a Spec for Ada DLLs
32805 @subsection Creating a Spec for Ada DLLs
32808 To use the services exported by the Ada DLL from another programming
32809 language (e.g.@: C), you have to translate the specs of the exported Ada
32810 entities in that language. For instance in the case of @code{API.dll},
32811 the corresponding C header file could look like:
32816 extern int *_imp__count;
32817 #define count (*_imp__count)
32818 int factorial (int);
32824 It is important to understand that when building an Ada DLL to be used by
32825 other Ada applications, you need two different specs for the packages
32826 contained in the DLL: one for building the DLL and the other for using
32827 the DLL. This is because the @code{DLL} calling convention is needed to
32828 use a variable defined in a DLL, but when building the DLL, the variable
32829 must have either the @code{Ada} or @code{C} calling convention. As an
32830 example consider a DLL comprising the following package @code{API}:
32832 @smallexample @c ada
32836 Count : Integer := 0;
32838 -- Remainder of the package omitted.
32845 After producing a DLL containing package @code{API}, the spec that
32846 must be used to import @code{API.Count} from Ada code outside of the
32849 @smallexample @c ada
32854 pragma Import (DLL, Count);
32860 @node Creating the Definition File
32861 @subsection Creating the Definition File
32864 The definition file is the last file needed to build the DLL. It lists
32865 the exported symbols. As an example, the definition file for a DLL
32866 containing only package @code{API} (where all the entities are exported
32867 with a @code{C} calling convention) is:
32882 If the @code{C} calling convention is missing from package @code{API},
32883 then the definition file contains the mangled Ada names of the above
32884 entities, which in this case are:
32893 api__initialize_api
32898 @node Using gnatdll
32899 @subsection Using @code{gnatdll}
32903 * gnatdll Example::
32904 * gnatdll behind the Scenes::
32909 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
32910 and non-Ada sources that make up your DLL have been compiled.
32911 @code{gnatdll} is actually in charge of two distinct tasks: build the
32912 static import library for the DLL and the actual DLL. The form of the
32913 @code{gnatdll} command is
32917 $ gnatdll @ovar{switches} @var{list-of-files} @r{[}-largs @var{opts}@r{]}
32922 where @var{list-of-files} is a list of ALI and object files. The object
32923 file list must be the exact list of objects corresponding to the non-Ada
32924 sources whose services are to be included in the DLL. The ALI file list
32925 must be the exact list of ALI files for the corresponding Ada sources
32926 whose services are to be included in the DLL. If @var{list-of-files} is
32927 missing, only the static import library is generated.
32930 You may specify any of the following switches to @code{gnatdll}:
32933 @item -a@ovar{address}
32934 @cindex @option{-a} (@code{gnatdll})
32935 Build a non-relocatable DLL at @var{address}. If @var{address} is not
32936 specified the default address @var{0x11000000} will be used. By default,
32937 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
32938 advise the reader to build relocatable DLL.
32940 @item -b @var{address}
32941 @cindex @option{-b} (@code{gnatdll})
32942 Set the relocatable DLL base address. By default the address is
32945 @item -bargs @var{opts}
32946 @cindex @option{-bargs} (@code{gnatdll})
32947 Binder options. Pass @var{opts} to the binder.
32949 @item -d @var{dllfile}
32950 @cindex @option{-d} (@code{gnatdll})
32951 @var{dllfile} is the name of the DLL. This switch must be present for
32952 @code{gnatdll} to do anything. The name of the generated import library is
32953 obtained algorithmically from @var{dllfile} as shown in the following
32954 example: if @var{dllfile} is @code{xyz.dll}, the import library name is
32955 @code{libxyz.dll.a}. The name of the definition file to use (if not specified
32956 by option @option{-e}) is obtained algorithmically from @var{dllfile}
32957 as shown in the following example:
32958 if @var{dllfile} is @code{xyz.dll}, the definition
32959 file used is @code{xyz.def}.
32961 @item -e @var{deffile}
32962 @cindex @option{-e} (@code{gnatdll})
32963 @var{deffile} is the name of the definition file.
32966 @cindex @option{-g} (@code{gnatdll})
32967 Generate debugging information. This information is stored in the object
32968 file and copied from there to the final DLL file by the linker,
32969 where it can be read by the debugger. You must use the
32970 @option{-g} switch if you plan on using the debugger or the symbolic
32974 @cindex @option{-h} (@code{gnatdll})
32975 Help mode. Displays @code{gnatdll} switch usage information.
32978 @cindex @option{-I} (@code{gnatdll})
32979 Direct @code{gnatdll} to search the @var{dir} directory for source and
32980 object files needed to build the DLL.
32981 (@pxref{Search Paths and the Run-Time Library (RTL)}).
32984 @cindex @option{-k} (@code{gnatdll})
32985 Removes the @code{@@}@var{nn} suffix from the import library's exported
32986 names, but keeps them for the link names. You must specify this
32987 option if you want to use a @code{Stdcall} function in a DLL for which
32988 the @code{@@}@var{nn} suffix has been removed. This is the case for most
32989 of the Windows NT DLL for example. This option has no effect when
32990 @option{-n} option is specified.
32992 @item -l @var{file}
32993 @cindex @option{-l} (@code{gnatdll})
32994 The list of ALI and object files used to build the DLL are listed in
32995 @var{file}, instead of being given in the command line. Each line in
32996 @var{file} contains the name of an ALI or object file.
32999 @cindex @option{-n} (@code{gnatdll})
33000 No Import. Do not create the import library.
33003 @cindex @option{-q} (@code{gnatdll})
33004 Quiet mode. Do not display unnecessary messages.
33007 @cindex @option{-v} (@code{gnatdll})
33008 Verbose mode. Display extra information.
33010 @item -largs @var{opts}
33011 @cindex @option{-largs} (@code{gnatdll})
33012 Linker options. Pass @var{opts} to the linker.
33015 @node gnatdll Example
33016 @subsubsection @code{gnatdll} Example
33019 As an example the command to build a relocatable DLL from @file{api.adb}
33020 once @file{api.adb} has been compiled and @file{api.def} created is
33023 $ gnatdll -d api.dll api.ali
33027 The above command creates two files: @file{libapi.dll.a} (the import
33028 library) and @file{api.dll} (the actual DLL). If you want to create
33029 only the DLL, just type:
33032 $ gnatdll -d api.dll -n api.ali
33036 Alternatively if you want to create just the import library, type:
33039 $ gnatdll -d api.dll
33042 @node gnatdll behind the Scenes
33043 @subsubsection @code{gnatdll} behind the Scenes
33046 This section details the steps involved in creating a DLL. @code{gnatdll}
33047 does these steps for you. Unless you are interested in understanding what
33048 goes on behind the scenes, you should skip this section.
33050 We use the previous example of a DLL containing the Ada package @code{API},
33051 to illustrate the steps necessary to build a DLL. The starting point is a
33052 set of objects that will make up the DLL and the corresponding ALI
33053 files. In the case of this example this means that @file{api.o} and
33054 @file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
33059 @code{gnatdll} builds the base file (@file{api.base}). A base file gives
33060 the information necessary to generate relocation information for the
33066 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
33071 In addition to the base file, the @command{gnatlink} command generates an
33072 output file @file{api.jnk} which can be discarded. The @option{-mdll} switch
33073 asks @command{gnatlink} to generate the routines @code{DllMain} and
33074 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
33075 is loaded into memory.
33078 @code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the
33079 export table (@file{api.exp}). The export table contains the relocation
33080 information in a form which can be used during the final link to ensure
33081 that the Windows loader is able to place the DLL anywhere in memory.
33085 $ dlltool --dllname api.dll --def api.def --base-file api.base \
33086 --output-exp api.exp
33091 @code{gnatdll} builds the base file using the new export table. Note that
33092 @command{gnatbind} must be called once again since the binder generated file
33093 has been deleted during the previous call to @command{gnatlink}.
33098 $ gnatlink api -o api.jnk api.exp -mdll
33099 -Wl,--base-file,api.base
33104 @code{gnatdll} builds the new export table using the new base file and
33105 generates the DLL import library @file{libAPI.dll.a}.
33109 $ dlltool --dllname api.dll --def api.def --base-file api.base \
33110 --output-exp api.exp --output-lib libAPI.a
33115 Finally @code{gnatdll} builds the relocatable DLL using the final export
33121 $ gnatlink api api.exp -o api.dll -mdll
33126 @node Using dlltool
33127 @subsubsection Using @code{dlltool}
33130 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
33131 DLLs and static import libraries. This section summarizes the most
33132 common @code{dlltool} switches. The form of the @code{dlltool} command
33136 $ dlltool @ovar{switches}
33140 @code{dlltool} switches include:
33143 @item --base-file @var{basefile}
33144 @cindex @option{--base-file} (@command{dlltool})
33145 Read the base file @var{basefile} generated by the linker. This switch
33146 is used to create a relocatable DLL.
33148 @item --def @var{deffile}
33149 @cindex @option{--def} (@command{dlltool})
33150 Read the definition file.
33152 @item --dllname @var{name}
33153 @cindex @option{--dllname} (@command{dlltool})
33154 Gives the name of the DLL. This switch is used to embed the name of the
33155 DLL in the static import library generated by @code{dlltool} with switch
33156 @option{--output-lib}.
33159 @cindex @option{-k} (@command{dlltool})
33160 Kill @code{@@}@var{nn} from exported names
33161 (@pxref{Windows Calling Conventions}
33162 for a discussion about @code{Stdcall}-style symbols.
33165 @cindex @option{--help} (@command{dlltool})
33166 Prints the @code{dlltool} switches with a concise description.
33168 @item --output-exp @var{exportfile}
33169 @cindex @option{--output-exp} (@command{dlltool})
33170 Generate an export file @var{exportfile}. The export file contains the
33171 export table (list of symbols in the DLL) and is used to create the DLL.
33173 @item --output-lib @var{libfile}
33174 @cindex @option{--output-lib} (@command{dlltool})
33175 Generate a static import library @var{libfile}.
33178 @cindex @option{-v} (@command{dlltool})
33181 @item --as @var{assembler-name}
33182 @cindex @option{--as} (@command{dlltool})
33183 Use @var{assembler-name} as the assembler. The default is @code{as}.
33186 @node GNAT and Windows Resources
33187 @section GNAT and Windows Resources
33188 @cindex Resources, windows
33191 * Building Resources::
33192 * Compiling Resources::
33193 * Using Resources::
33197 Resources are an easy way to add Windows specific objects to your
33198 application. The objects that can be added as resources include:
33227 This section explains how to build, compile and use resources.
33229 @node Building Resources
33230 @subsection Building Resources
33231 @cindex Resources, building
33234 A resource file is an ASCII file. By convention resource files have an
33235 @file{.rc} extension.
33236 The easiest way to build a resource file is to use Microsoft tools
33237 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
33238 @code{dlgedit.exe} to build dialogs.
33239 It is always possible to build an @file{.rc} file yourself by writing a
33242 It is not our objective to explain how to write a resource file. A
33243 complete description of the resource script language can be found in the
33244 Microsoft documentation.
33246 @node Compiling Resources
33247 @subsection Compiling Resources
33250 @cindex Resources, compiling
33253 This section describes how to build a GNAT-compatible (COFF) object file
33254 containing the resources. This is done using the Resource Compiler
33255 @code{windres} as follows:
33258 $ windres -i myres.rc -o myres.o
33262 By default @code{windres} will run @command{gcc} to preprocess the @file{.rc}
33263 file. You can specify an alternate preprocessor (usually named
33264 @file{cpp.exe}) using the @code{windres} @option{--preprocessor}
33265 parameter. A list of all possible options may be obtained by entering
33266 the command @code{windres} @option{--help}.
33268 It is also possible to use the Microsoft resource compiler @code{rc.exe}
33269 to produce a @file{.res} file (binary resource file). See the
33270 corresponding Microsoft documentation for further details. In this case
33271 you need to use @code{windres} to translate the @file{.res} file to a
33272 GNAT-compatible object file as follows:
33275 $ windres -i myres.res -o myres.o
33278 @node Using Resources
33279 @subsection Using Resources
33280 @cindex Resources, using
33283 To include the resource file in your program just add the
33284 GNAT-compatible object file for the resource(s) to the linker
33285 arguments. With @command{gnatmake} this is done by using the @option{-largs}
33289 $ gnatmake myprog -largs myres.o
33292 @node Debugging a DLL
33293 @section Debugging a DLL
33294 @cindex DLL debugging
33297 * Program and DLL Both Built with GCC/GNAT::
33298 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
33302 Debugging a DLL is similar to debugging a standard program. But
33303 we have to deal with two different executable parts: the DLL and the
33304 program that uses it. We have the following four possibilities:
33308 The program and the DLL are built with @code{GCC/GNAT}.
33310 The program is built with foreign tools and the DLL is built with
33313 The program is built with @code{GCC/GNAT} and the DLL is built with
33319 In this section we address only cases one and two above.
33320 There is no point in trying to debug
33321 a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging
33322 information in it. To do so you must use a debugger compatible with the
33323 tools suite used to build the DLL.
33325 @node Program and DLL Both Built with GCC/GNAT
33326 @subsection Program and DLL Both Built with GCC/GNAT
33329 This is the simplest case. Both the DLL and the program have @code{GDB}
33330 compatible debugging information. It is then possible to break anywhere in
33331 the process. Let's suppose here that the main procedure is named
33332 @code{ada_main} and that in the DLL there is an entry point named
33336 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and
33337 program must have been built with the debugging information (see GNAT -g
33338 switch). Here are the step-by-step instructions for debugging it:
33341 @item Launch @code{GDB} on the main program.
33347 @item Start the program and stop at the beginning of the main procedure
33354 This step is required to be able to set a breakpoint inside the DLL. As long
33355 as the program is not run, the DLL is not loaded. This has the
33356 consequence that the DLL debugging information is also not loaded, so it is not
33357 possible to set a breakpoint in the DLL.
33359 @item Set a breakpoint inside the DLL
33362 (gdb) break ada_dll
33369 At this stage a breakpoint is set inside the DLL. From there on
33370 you can use the standard approach to debug the whole program
33371 (@pxref{Running and Debugging Ada Programs}).
33374 @c This used to work, probably because the DLLs were non-relocatable
33375 @c keep this section around until the problem is sorted out.
33377 To break on the @code{DllMain} routine it is not possible to follow
33378 the procedure above. At the time the program stop on @code{ada_main}
33379 the @code{DllMain} routine as already been called. Either you can use
33380 the procedure below @pxref{Debugging the DLL Directly} or this procedure:
33383 @item Launch @code{GDB} on the main program.
33389 @item Load DLL symbols
33392 (gdb) add-sym api.dll
33395 @item Set a breakpoint inside the DLL
33398 (gdb) break ada_dll.adb:45
33401 Note that at this point it is not possible to break using the routine symbol
33402 directly as the program is not yet running. The solution is to break
33403 on the proper line (break in @file{ada_dll.adb} line 45).
33405 @item Start the program
33414 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT
33415 @subsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
33418 * Debugging the DLL Directly::
33419 * Attaching to a Running Process::
33423 In this case things are slightly more complex because it is not possible to
33424 start the main program and then break at the beginning to load the DLL and the
33425 associated DLL debugging information. It is not possible to break at the
33426 beginning of the program because there is no @code{GDB} debugging information,
33427 and therefore there is no direct way of getting initial control. This
33428 section addresses this issue by describing some methods that can be used
33429 to break somewhere in the DLL to debug it.
33432 First suppose that the main procedure is named @code{main} (this is for
33433 example some C code built with Microsoft Visual C) and that there is a
33434 DLL named @code{test.dll} containing an Ada entry point named
33438 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have
33439 been built with debugging information (see GNAT -g option).
33441 @node Debugging the DLL Directly
33442 @subsubsection Debugging the DLL Directly
33446 Find out the executable starting address
33449 $ objdump --file-header main.exe
33452 The starting address is reported on the last line. For example:
33455 main.exe: file format pei-i386
33456 architecture: i386, flags 0x0000010a:
33457 EXEC_P, HAS_DEBUG, D_PAGED
33458 start address 0x00401010
33462 Launch the debugger on the executable.
33469 Set a breakpoint at the starting address, and launch the program.
33472 $ (gdb) break *0x00401010
33476 The program will stop at the given address.
33479 Set a breakpoint on a DLL subroutine.
33482 (gdb) break ada_dll.adb:45
33485 Or if you want to break using a symbol on the DLL, you need first to
33486 select the Ada language (language used by the DLL).
33489 (gdb) set language ada
33490 (gdb) break ada_dll
33494 Continue the program.
33501 This will run the program until it reaches the breakpoint that has been
33502 set. From that point you can use the standard way to debug a program
33503 as described in (@pxref{Running and Debugging Ada Programs}).
33508 It is also possible to debug the DLL by attaching to a running process.
33510 @node Attaching to a Running Process
33511 @subsubsection Attaching to a Running Process
33512 @cindex DLL debugging, attach to process
33515 With @code{GDB} it is always possible to debug a running process by
33516 attaching to it. It is possible to debug a DLL this way. The limitation
33517 of this approach is that the DLL must run long enough to perform the
33518 attach operation. It may be useful for instance to insert a time wasting
33519 loop in the code of the DLL to meet this criterion.
33523 @item Launch the main program @file{main.exe}.
33529 @item Use the Windows @i{Task Manager} to find the process ID. Let's say
33530 that the process PID for @file{main.exe} is 208.
33538 @item Attach to the running process to be debugged.
33544 @item Load the process debugging information.
33547 (gdb) symbol-file main.exe
33550 @item Break somewhere in the DLL.
33553 (gdb) break ada_dll
33556 @item Continue process execution.
33565 This last step will resume the process execution, and stop at
33566 the breakpoint we have set. From there you can use the standard
33567 approach to debug a program as described in
33568 (@pxref{Running and Debugging Ada Programs}).
33570 @node Setting Stack Size from gnatlink
33571 @section Setting Stack Size from @command{gnatlink}
33574 It is possible to specify the program stack size at link time. On modern
33575 versions of Windows, starting with XP, this is mostly useful to set the size of
33576 the main stack (environment task). The other task stacks are set with pragma
33577 Storage_Size or with the @command{gnatbind -d} command.
33579 Since older versions of Windows (2000, NT4, etc.) do not allow setting the
33580 reserve size of individual tasks, the link-time stack size applies to all
33581 tasks, and pragma Storage_Size has no effect.
33582 In particular, Stack Overflow checks are made against this
33583 link-time specified size.
33585 This setting can be done with
33586 @command{gnatlink} using either:
33590 @item using @option{-Xlinker} linker option
33593 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
33596 This sets the stack reserve size to 0x10000 bytes and the stack commit
33597 size to 0x1000 bytes.
33599 @item using @option{-Wl} linker option
33602 $ gnatlink hello -Wl,--stack=0x1000000
33605 This sets the stack reserve size to 0x1000000 bytes. Note that with
33606 @option{-Wl} option it is not possible to set the stack commit size
33607 because the coma is a separator for this option.
33611 @node Setting Heap Size from gnatlink
33612 @section Setting Heap Size from @command{gnatlink}
33615 Under Windows systems, it is possible to specify the program heap size from
33616 @command{gnatlink} using either:
33620 @item using @option{-Xlinker} linker option
33623 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
33626 This sets the heap reserve size to 0x10000 bytes and the heap commit
33627 size to 0x1000 bytes.
33629 @item using @option{-Wl} linker option
33632 $ gnatlink hello -Wl,--heap=0x1000000
33635 This sets the heap reserve size to 0x1000000 bytes. Note that with
33636 @option{-Wl} option it is not possible to set the heap commit size
33637 because the coma is a separator for this option.
33643 @c **********************************
33644 @c * GNU Free Documentation License *
33645 @c **********************************
33647 @c GNU Free Documentation License
33649 @node Index,,GNU Free Documentation License, Top
33655 @c Put table of contents at end, otherwise it precedes the "title page" in
33656 @c the .txt version
33657 @c Edit the pdf file to move the contents to the beginning, after the title